diff --git a/cpp/src/arrow/array/validate.cc b/cpp/src/arrow/array/validate.cc
index 6ac885f8443c6..cfbabfaeef0d5 100644
--- a/cpp/src/arrow/array/validate.cc
+++ b/cpp/src/arrow/array/validate.cc
@@ -204,7 +204,7 @@ struct ValidateArrayImpl {
         return Status::Invalid("Negative offsets in binary array");
       }
       const auto data_extent = last_offset - first_offset;
-      const auto values_length = values.size();
+      const auto values_length = values.capacity();
       if (values_length < data_extent) {
         return Status::Invalid("Length spanned by binary offsets (", data_extent,
                                ") larger than values array (size ", values_length, ")");
diff --git a/cpp/src/parquet/column_reader.cc b/cpp/src/parquet/column_reader.cc
index f4979d2d97f57..56f87b74569fd 100644
--- a/cpp/src/parquet/column_reader.cc
+++ b/cpp/src/parquet/column_reader.cc
@@ -1641,7 +1641,7 @@ class ByteArrayChunkedRecordReader : public TypedRecordReader<ByteArrayType>,
       int64_t binary_length = last_offset - first_offset;
       // std::cout << "binary_length:" << binary_length << std::endl;
       values_->SetSize(binary_length);
-    
+
       offset_ = AllocateBuffer(this->pool_);
       bianry_length_ = 0;
       return result;