diff --git a/src/encoding/json/jsontext/decode.go b/src/encoding/json/jsontext/decode.go
index f505de44684..511832f2ae0 100644
--- a/src/encoding/json/jsontext/decode.go
+++ b/src/encoding/json/jsontext/decode.go
@@ -792,6 +792,12 @@ func (d *decoderState) CheckNextValue(last bool) error {
 	return nil
 }
 
+// AtEOF reports whether the decoder is at EOF.
+func (d *decoderState) AtEOF() bool {
+	_, err := d.consumeWhitespace(d.prevEnd)
+	return err == io.ErrUnexpectedEOF
+}
+
 // CheckEOF verifies that the input has no more data.
 func (d *decoderState) CheckEOF() error {
 	return d.checkEOF(d.prevEnd)
diff --git a/src/encoding/json/v2/arshal.go b/src/encoding/json/v2/arshal.go
index 6b4bcb0c74c..573d26567f3 100644
--- a/src/encoding/json/v2/arshal.go
+++ b/src/encoding/json/v2/arshal.go
@@ -440,8 +440,9 @@ func UnmarshalRead(in io.Reader, out any, opts ...Options) (err error) {
 // Unlike [Unmarshal] and [UnmarshalRead], decode options are ignored because
 // they must have already been specified on the provided [jsontext.Decoder].
 //
-// The input may be a stream of one or more JSON values,
+// The input may be a stream of zero or more JSON values,
 // where this only unmarshals the next JSON value in the stream.
+// If there are no more top-level JSON values, it reports [io.EOF].
 // The output must be a non-nil pointer.
 // See [Unmarshal] for details about the conversion of JSON into a Go value.
 func UnmarshalDecode(in *jsontext.Decoder, out any, opts ...Options) (err error) {
diff --git a/src/encoding/json/v2/arshal_funcs.go b/src/encoding/json/v2/arshal_funcs.go
index 673caf3c376..28916af948d 100644
--- a/src/encoding/json/v2/arshal_funcs.go
+++ b/src/encoding/json/v2/arshal_funcs.go
@@ -9,6 +9,7 @@ package json
 import (
 	"errors"
 	"fmt"
+	"io"
 	"reflect"
 	"sync"
 
@@ -306,6 +307,9 @@ func UnmarshalFromFunc[T any](fn func(*jsontext.Decoder, T) error) *Unmarshalers
 		fnc: func(dec *jsontext.Decoder, va addressableValue, uo *jsonopts.Struct) error {
 			xd := export.Decoder(dec)
 			prevDepth, prevLength := xd.Tokens.DepthLength()
+			if prevDepth == 1 && xd.AtEOF() {
+				return io.EOF // check EOF early to avoid fn reporting an EOF
+			}
 			xd.Flags.Set(jsonflags.WithinArshalCall | 1)
 			v, _ := reflect.TypeAssert[T](va.castTo(t))
 			err := fn(dec, v)
diff --git a/src/encoding/json/v2/arshal_methods.go b/src/encoding/json/v2/arshal_methods.go
index 2decd144dbe..1621eadc080 100644
--- a/src/encoding/json/v2/arshal_methods.go
+++ b/src/encoding/json/v2/arshal_methods.go
@@ -9,6 +9,7 @@ package json
 import (
 	"encoding"
 	"errors"
+	"io"
 	"reflect"
 
 	"encoding/json/internal"
@@ -302,6 +303,9 @@ func makeMethodArshaler(fncs *arshaler, t reflect.Type) *arshaler {
 			}
 			xd := export.Decoder(dec)
 			prevDepth, prevLength := xd.Tokens.DepthLength()
+			if prevDepth == 1 && xd.AtEOF() {
+				return io.EOF // check EOF early to avoid fn reporting an EOF
+			}
 			xd.Flags.Set(jsonflags.WithinArshalCall | 1)
 			unmarshaler, _ := reflect.TypeAssert[UnmarshalerFrom](va.Addr())
 			err := unmarshaler.UnmarshalJSONFrom(dec)
diff --git a/src/encoding/json/v2/arshal_test.go b/src/encoding/json/v2/arshal_test.go
index 75093345a3b..dc15c5a5f53 100644
--- a/src/encoding/json/v2/arshal_test.go
+++ b/src/encoding/json/v2/arshal_test.go
@@ -7833,7 +7833,8 @@ func TestUnmarshal(t *testing.T) {
 		})),
 		wantErr: EU(errSomeError).withType(0, T[unmarshalJSONv2Func]()),
 	}, {
-		name: jsontest.Name("Methods/Invalid/JSONv2/TooFew"),
+		name:  jsontest.Name("Methods/Invalid/JSONv2/TooFew"),
+		inBuf: `{}`,
 		inVal: addr(unmarshalJSONv2Func(func(*jsontext.Decoder) error {
 			return nil // do nothing
 		})),
@@ -9234,6 +9235,43 @@ func TestUnmarshalReuse(t *testing.T) {
 	})
 }
 
+type unmarshalerEOF struct{}
+
+func (unmarshalerEOF) UnmarshalJSONFrom(dec *jsontext.Decoder) error {
+	return io.EOF // should be wrapped and converted by Unmarshal to io.ErrUnexpectedEOF
+}
+
+// TestUnmarshalEOF verifies that io.EOF is only ever returned by
+// UnmarshalDecode for a top-level value.
+func TestUnmarshalEOF(t *testing.T) {
+	opts := WithUnmarshalers(UnmarshalFromFunc(func(dec *jsontext.Decoder, _ *struct{}) error {
+		return io.EOF // should be wrapped and converted by Unmarshal to io.ErrUnexpectedEOF
+	}))
+
+	for _, in := range []string{"", "[", "[null", "[null]"} {
+		for _, newOut := range []func() any{
+			func() any { return new(unmarshalerEOF) },
+			func() any { return new([]unmarshalerEOF) },
+			func() any { return new(struct{}) },
+			func() any { return new([]struct{}) },
+		} {
+			wantErr := io.ErrUnexpectedEOF
+			if gotErr := Unmarshal([]byte(in), newOut(), opts); !errors.Is(gotErr, wantErr) {
+				t.Errorf("Unmarshal = %v, want %v", gotErr, wantErr)
+			}
+			if gotErr := UnmarshalRead(strings.NewReader(in), newOut(), opts); !errors.Is(gotErr, wantErr) {
+				t.Errorf("Unmarshal = %v, want %v", gotErr, wantErr)
+			}
+			switch gotErr := UnmarshalDecode(jsontext.NewDecoder(strings.NewReader(in)), newOut(), opts); {
+			case in != "" && !errors.Is(gotErr, wantErr):
+				t.Errorf("Unmarshal = %v, want %v", gotErr, wantErr)
+			case in == "" && gotErr != io.EOF:
+				t.Errorf("Unmarshal = %v, want %v", gotErr, io.EOF)
+			}
+		}
+	}
+}
+
 type ReaderFunc func([]byte) (int, error)
 
 func (f ReaderFunc) Read(b []byte) (int, error) { return f(b) }
diff --git a/src/encoding/json/v2/errors.go b/src/encoding/json/v2/errors.go
index 0f50d608c9e..4421f8b821c 100644
--- a/src/encoding/json/v2/errors.go
+++ b/src/encoding/json/v2/errors.go
@@ -10,6 +10,7 @@ import (
 	"cmp"
 	"errors"
 	"fmt"
+	"io"
 	"reflect"
 	"strconv"
 	"strings"
@@ -118,7 +119,7 @@ func newInvalidFormatError(c coder, t reflect.Type) error {
 // newMarshalErrorBefore wraps err in a SemanticError assuming that e
 // is positioned right before the next token or value, which causes an error.
 func newMarshalErrorBefore(e *jsontext.Encoder, t reflect.Type, err error) error {
-	return &SemanticError{action: "marshal", GoType: t, Err: err,
+	return &SemanticError{action: "marshal", GoType: t, Err: toUnexpectedEOF(err),
 		ByteOffset:  e.OutputOffset() + int64(export.Encoder(e).CountNextDelimWhitespace()),
 		JSONPointer: jsontext.Pointer(export.Encoder(e).AppendStackPointer(nil, +1))}
 }
@@ -134,7 +135,7 @@ func newUnmarshalErrorBefore(d *jsontext.Decoder, t reflect.Type, err error) err
 	if export.Decoder(d).Flags.Get(jsonflags.ReportErrorsWithLegacySemantics) {
 		k = d.PeekKind()
 	}
-	return &SemanticError{action: "unmarshal", GoType: t, Err: err,
+	return &SemanticError{action: "unmarshal", GoType: t, Err: toUnexpectedEOF(err),
 		ByteOffset:  d.InputOffset() + int64(export.Decoder(d).CountNextDelimWhitespace()),
 		JSONPointer: jsontext.Pointer(export.Decoder(d).AppendStackPointer(nil, +1)),
 		JSONKind:    k}
@@ -157,7 +158,7 @@ func newUnmarshalErrorBeforeWithSkipping(d *jsontext.Decoder, t reflect.Type, er
 // is positioned right after the previous token or value, which caused an error.
 func newUnmarshalErrorAfter(d *jsontext.Decoder, t reflect.Type, err error) error {
 	tokOrVal := export.Decoder(d).PreviousTokenOrValue()
-	return &SemanticError{action: "unmarshal", GoType: t, Err: err,
+	return &SemanticError{action: "unmarshal", GoType: t, Err: toUnexpectedEOF(err),
 		ByteOffset:  d.InputOffset() - int64(len(tokOrVal)),
 		JSONPointer: jsontext.Pointer(export.Decoder(d).AppendStackPointer(nil, -1)),
 		JSONKind:    jsontext.Value(tokOrVal).Kind()}
@@ -206,6 +207,7 @@ func newSemanticErrorWithPosition(c coder, t reflect.Type, prevDepth int, prevLe
 	if serr == nil {
 		serr = &SemanticError{Err: err}
 	}
+	serr.Err = toUnexpectedEOF(serr.Err)
 	var currDepth int
 	var currLength int64
 	var coderState interface{ AppendStackPointer([]byte, int) []byte }
@@ -432,3 +434,11 @@ func newDuplicateNameError(ptr jsontext.Pointer, quotedName []byte, offset int64
 		Err:         jsontext.ErrDuplicateName,
 	}
 }
+
+// toUnexpectedEOF converts [io.EOF] to [io.ErrUnexpectedEOF].
+func toUnexpectedEOF(err error) error {
+	if err == io.EOF {
+		return io.ErrUnexpectedEOF
+	}
+	return err
+}