19 teams are tied for the best ERA in a month, with an ERA of 0.00. The first three are the Pittsburgh Pirates 4 times, the Boston Red Sox in October 2023 and in October 2006 and the Chicago White Sox in October 2023.

	TEAM	ERA	MONTH	G	W%	W	L	SO	SHO	SV	IP	H	ER	R	HR	BB	HBP	IBB	TBF	WP	K/9	BB/9	K/BB	HR/9	K%	BB%	WHIP	BABIP	RA	H/9
1	Pirates	0.00	October 2023	1	1.000	1	0	11	0	1	9.0	3	0	0	0	1	0	0	30	1	11.00	1.00	11.00	0.00	36.7	3.3	0.44	.167	0.00	3.00
2	Red Sox	0.00	October 2023	1	1.000	1	0	9	0	0	9.0	2	0	1	0	4	0	0	33	0	9.00	4.00	2.25	0.00	27.3	12.1	0.67	.100	1.00	2.00
3	White Sox	0.00	October 2023	1	.000	0	1	8	0	0	11.0	7	0	2	0	7	0	0	44	0	6.55	5.73	1.14	0.00	18.2	15.9	1.27	.241	1.64	5.73
4	Padres	0.00	October 2023	1	1.000	1	0	16	0	0	11.0	7	0	1	0	3	1	1	44	0	13.09	2.45	5.33	0.00	36.4	6.8	0.91	.292	0.82	5.73
5	Brewers	0.00	October 2023	1	1.000	1	0	8	0	0	9.0	5	0	0	0	2	0	0	34	0	8.00	2.00	4.00	0.00	23.5	5.9	0.78	.208	0.00	5.00
6	Mariners	0.00	October 2023	1	1.000	1	0	11	0	1	9.0	4	0	0	0	0	0	0	30	0	11.00	0.00		0.00	36.7	0.0	0.44	.211	0.00	4.00
7	Cubs	0.00	March 2023	1	1.000	1	0	12	0	0	9.0	4	0	0	0	5	0	0	34	1	12.00	5.00	2.40	0.00	35.3	14.7	1.00	.235	0.00	4.00
8	Twins	0.00	March 2023	1	1.000	1	0	11	0	1	9.0	2	0	0	0	5	1	0	33	0	11.00	5.00	2.20	0.00	33.3	15.2	0.78	.125	0.00	2.00
9	Yankees	0.00	March 2023	1	1.000	1	0	16	0	0	9.0	4	0	0	0	3	0	0	33	0	16.00	3.00	5.33	0.00	48.5	9.1	0.78	.286	0.00	4.00
10	Rays	0.00	March 2023	1	1.000	1	0	6	0	0	9.0	6	0	0	0	3	0	0	35	0	6.00	3.00	2.00	0.00	17.1	8.6	1.00	.231	0.00	6.00
11	Phillies	0.00	October 2017	1	1.000	1	0	11	0	0	9.0	2	0	0	0	5	1	0	35	1	11.00	5.00	2.20	0.00	31.4	14.3	0.78	.111	0.00	2.00
12	Rays	0.00	October 2017	1	1.000	1	0	18	0	0	9.0	3	0	0	0	0	0	0	31	2	18.00	0.00		0.00	58.1	0.0	0.33	.231	0.00	3.00
13	Pirates	0.00	March 2014	1	1.000	1	0	11	0	0	10.0	6	0	0	0	4	0	0	38	0	9.90	3.60	2.75	0.00	28.9	10.5	1.00	.261	0.00	5.40
14	Cardinals	0.00	March 2014	1	1.000	1	0	12	0	1	9.0	3	0	0	0	5	0	1	36	1	12.00	5.00	2.40	0.00	33.3	13.9	0.89	.158	0.00	3.00
15	Indians	0.00	March 2014	1	1.000	1	0	7	0	1	9.0	5	0	0	0	4	0	0	36	2	7.00	4.00	1.75	0.00	19.4	11.1	1.00	.200	0.00	5.00
16	Brewers	0.00	March 2014	1	1.000	1	0	7	0	1	9.0	5	0	0	0	2	0	0	34	0	7.00	2.00	3.50	0.00	20.6	5.9	0.78	.200	0.00	5.00
17	Braves	0.00	March 2011	1	1.000	1	0	9	0	1	9.0	5	0	0	0	2	0	0	33	0	9.00	2.00	4.50	0.00	27.3	6.1	0.78	.227	0.00	5.00
18	Dodgers	0.00	March 2008	1	1.000	1	0	4	0	0	9.0	5	0	0	0	3	0	0	32	0	4.00	3.00	1.33	0.00	12.5	9.4	0.89	.200	0.00	5.00
19	Padres	0.00	March 2008	1	1.000	1	0	4	0	0	9.0	4	0	0	0	4	0	0	34	0	4.00	4.00	1.00	0.00	11.8	11.8	0.89	.154	0.00	4.00
20	Pirates	0.00	October 2006	1	1.000	1	0	4	0	1	9.0	4	0	0	0	2	0	0	33	1	4.00	2.00	2.00	0.00	12.1	6.1	0.67	.148	0.00	4.00
21	Red Sox	0.00	October 2006	1	1.000	1	0	6	1	0	5.0	0	0	0	0	1	0	0	15	0	10.80	1.80	6.00	0.00	40.0	6.7	0.20	.000	0.00	0.00
22	Pirates	0.00	March 2003	1	1.000	1	0	4	0	0	9.0	4	0	1	0	3	0	0	35	0	4.00	3.00	1.33	0.00	11.4	8.6	0.78	.143	1.00	4.00
23	Dodgers	0.00	March 2003	1	1.000	1	0	7	1	0	9.0	4	0	0	0	1	0	0	30	0	7.00	1.00	7.00	0.00	23.3	3.3	0.56	.182	0.00	4.00
24	Royals	0.00	March 2003	1	1.000	1	0	8	0	1	9.0	3	0	0	0	2	0	0	31	0	8.00	2.00	4.00	0.00	25.8	6.5	0.56	.143	0.00	3.00
25	Indians	0.00	March 2002	1	1.000	1	0	5	1	0	9.0	5	0	0	0	2	0	0	33	0	5.00	2.00	2.50	0.00	15.2	6.1	0.78	.192	0.00	5.00