diff --git a/cpp/src/parquet/page_index.cc b/cpp/src/parquet/page_index.cc
index b9959f8b4aaf2..b60b5ffcaf659 100644
--- a/cpp/src/parquet/page_index.cc
+++ b/cpp/src/parquet/page_index.cc
@@ -696,7 +696,7 @@ class OffsetIndexBuilderImpl final : public OffsetIndexBuilder {
         if (offset_index_.page_locations.size() ==
             offset_index_.unencoded_byte_array_data_bytes.size()) {
           offset_index_.__isset.unencoded_byte_array_data_bytes = true;
-        } else {
+        } else if (!offset_index_.unencoded_byte_array_data_bytes.empty()) {
           std::stringstream ss;
           ss << "Invalid count of unencoded BYTE_ARRAY data bytes: "
              << offset_index_.unencoded_byte_array_data_bytes.size()