diff --git a/cpp/src/arrow/memory_pool.cc b/cpp/src/arrow/memory_pool.cc
index 34bd600e..3ef32090 100644
--- a/cpp/src/arrow/memory_pool.cc
+++ b/cpp/src/arrow/memory_pool.cc
@@ -53,6 +53,7 @@ Status AllocateAligned(int64_t size, uint8_t** out) {
     ss << "malloc of size " << size << " failed";
     return Status::OutOfMemory(ss.str());
   }
+  memset(*out, 0, size);
 #elif defined(ARROW_JEMALLOC)
   *out = reinterpret_cast<uint8_t*>(mallocx(
       std::max(static_cast<size_t>(size), kAlignment), MALLOCX_ALIGN(kAlignment)));
@@ -75,6 +76,7 @@ Status AllocateAligned(int64_t size, uint8_t** out) {
     ss << "invalid alignment parameter: " << kAlignment;
     return Status::Invalid(ss.str());
   }
+  memset(*out, 0, size);
 #endif
   return Status::OK();
 }
@@ -124,6 +126,9 @@ class DefaultMemoryPool : public MemoryPool {
     DCHECK(out);
     // Copy contents and release old memory chunk
     memcpy(out, *ptr, static_cast<size_t>(std::min(new_size, old_size)));
+    if (new_size > old_size) {
+      memset(out + old_size, 0, static_cast<size_t>(new_size - old_size));
+    }
 #ifdef _MSC_VER
     _aligned_free(*ptr);
 #else