The St. Louis Cardinals and the Tampa Bay Rays were tied for the most wins in a month in 2021, with 22 wins.

	TEAM	W	MONTH	L	W%	G	AB	R	H	2B	3B	HR	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Cardinals	22	September 2021	7	.759	29	952	158	251	50	2	52	151	69	12	253	19	1	1,057	461	104	10	14	4	17	.264	.317	.484	.801
2	Rays	22	May 2021	6	.786	28	963	160	228	53	3	40	153	120	14	311	23	8	1,100	407	96	1	2	7	12	.237	.329	.423	.752
3	Giants	21	September 2021	6	.778	27	937	158	260	61	6	39	149	114	16	226	11	3	1,081	450	106	7	7	11	22	.277	.363	.480	.843
4	Dodgers	21	August 2021	6	.778	27	911	129	215	47	2	41	126	94	18	249	15	3	1,035	389	90	3	9	8	9	.236	.317	.427	.744
5	Yankees	21	August 2021	8	.724	29	965	154	243	50	3	41	146	111	16	268	20	4	1,101	422	94	0	9	5	22	.252	.336	.437	.773
6	Rays	21	August 2021	6	.778	27	931	182	242	56	7	44	169	93	8	235	7	3	1,043	444	107	1	10	8	12	.260	.329	.477	.806
7	Dodgers	19	September 2021	7	.731	26	855	128	211	37	3	43	124	89	12	196	13	6	977	383	83	8	13	4	17	.247	.322	.448	.770
8	Blue Jays	19	September 2021	9	.679	28	953	167	261	58	2	55	163	97	10	196	15	2	1,070	488	115	1	9	0	12	.274	.344	.512	.856
9	Giants	19	August 2021	9	.679	28	967	125	232	45	2	43	122	80	10	236	11	2	1,064	410	90	4	3	7	15	.240	.304	.424	.728
10	Brewers	19	August 2021	9	.679	28	933	138	239	54	5	34	128	83	16	203	12	2	1,043	405	93	3	8	6	13	.256	.325	.434	.759
11	Astros	19	June 2021	9	.679	28	956	170	281	55	1	43	167	126	15	224	12	4	1,116	467	99	1	18	2	28	.294	.378	.488	.867
12	Nationals	19	June 2021	9	.679	28	895	131	230	45	3	40	126	94	14	244	15	3	1,014	401	88	7	4	5	32	.257	.336	.448	.784
13	Brewers	19	June 2021	8	.704	27	881	147	205	46	2	39	138	118	17	252	13	4	1,030	372	87	7	7	8	17	.233	.332	.422	.755
14	Cubs	19	May 2021	8	.704	27	904	131	238	39	3	35	126	87	15	244	16	8	1,022	388	77	9	7	5	19	.263	.336	.429	.765
15	White Sox	19	May 2021	10	.655	29	909	140	224	45	7	30	133	123	16	264	8	5	1,067	373	82	9	10	1	19	.246	.343	.410	.753
16	Padres	19	May 2021	9	.679	28	936	155	225	42	7	31	145	110	12	217	26	8	1,074	374	80	5	11	7	18	.240	.325	.400	.724
17	Mariners	18	September 2021	8	.692	26	885	130	213	46	2	32	126	89	13	206	10	5	994	359	80	0	7	2	22	.241	.317	.406	.723
18	Braves	18	August 2021	8	.692	26	882	134	213	31	4	43	128	96	9	212	10	0	999	381	78	6	6	5	13	.241	.320	.432	.752
19	Red Sox	18	June 2021	10	.643	28	945	141	245	54	5	33	136	84	14	240	8	6	1,057	408	92	2	12	2	12	.259	.325	.432	.757
20	Giants	18	May 2021	10	.643	28	927	155	219	38	4	46	144	123	11	287	9	6	1,075	403	88	10	4	7	19	.236	.331	.435	.766
21	Phillies	17	August 2021	11	.607	28	949	142	234	52	10	39	135	99	12	211	7	5	1,074	423	101	8	6	10	14	.247	.324	.446	.769
22	Dodgers	17	June 2021	9	.654	26	834	120	191	33	4	34	111	111	17	207	7	2	974	334	71	7	5	2	22	.229	.330	.400	.730
23	Athletics	17	June 2021	9	.654	26	880	140	224	45	4	33	135	85	14	205	8	0	994	376	82	4	11	3	6	.255	.326	.427	.754
24	Indians	17	May 2021	12	.586	29	924	114	209	43	4	31	107	85	12	243	13	4	1,031	353	78	7	3	5	28	.226	.299	.382	.681
25	Yankees	17	May 2021	11	.607	28	891	100	208	27	2	25	87	100	9	268	8	3	1,006	314	54	0	6	2	28	.233	.315	.352	.668