diff --git a/pandas/_libs/writers.pyx b/pandas/_libs/writers.pyx
index 73201e75c3c88..e841ff7819347 100644
--- a/pandas/_libs/writers.pyx
+++ b/pandas/_libs/writers.pyx
@@ -107,7 +107,7 @@ 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 bb5bce96bc64b..2a6a7089d77fb 100644
--- a/pandas/io/sas/sas.pyx
+++ b/pandas/io/sas/sas.pyx
@@ -436,7 +436,7 @@ 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