diff --git a/pandas/_libs/writers.pyx b/pandas/_libs/writers.pyx
index 091d76df26a17..2d5b31d7ccbcf 100644
--- a/pandas/_libs/writers.pyx
+++ b/pandas/_libs/writers.pyx
@@ -112,7 +112,7 @@ def convert_json_to_lines(arr: object) -> str:
             if not in_quotes:
                 num_open_brackets_seen -= 1
 
-    return narr.tostring().decode('utf-8')
+    return narr.tobytes().decode('utf-8')
 
 
 # stata, pytables
diff --git a/pandas/io/sas/sas.pyx b/pandas/io/sas/sas.pyx
index 11171af1e0c82..0038e39e2ffcc 100644
--- a/pandas/io/sas/sas.pyx
+++ b/pandas/io/sas/sas.pyx
@@ -431,7 +431,7 @@ cdef class Parser:
             elif column_types[j] == column_type_string:
                 # string
                 string_chunk[js, current_row] = np.array(source[start:(
-                    start + lngt)]).tostring().rstrip(b"\x00 ")
+                    start + lngt)]).tobytes().rstrip(b"\x00 ")
                 js += 1
 
         self.current_row_on_page_index += 1