The St. Louis Cardinals had the best ERA by a team in 2015, with an ERA of 2.94.

	TEAM	ERA	SEASON	G	W%	W	L	GS	SO	CG	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	Cardinals	2.94	2015	162	.617	100	62	162	1,329	1	0	62	1464.2	1,359	478	525	123	477	45	37	6,134	48	8.17	2.93	2.79	0.76	21.7	7.8	1.25	.297	3.23	8.35
2	Pirates	3.21	2015	162	.605	98	64	162	1,338	0	0	54	1489.2	1,392	532	596	110	453	75	38	6,215	67	8.08	2.74	2.95	0.66	21.5	7.3	1.24	.302	3.60	8.41
3	Cubs	3.36	2015	162	.599	97	65	162	1,431	6	4	48	1461.1	1,276	546	608	134	407	46	38	5,997	66	8.81	2.51	3.52	0.83	23.9	6.8	1.15	.287	3.74	7.86
4	Mets	3.43	2015	162	.556	90	72	162	1,337	1	1	50	1462.2	1,341	557	613	152	383	44	43	6,046	46	8.23	2.36	3.49	0.94	22.1	6.3	1.18	.288	3.77	8.25
5	Dodgers	3.44	2015	162	.568	92	70	162	1,396	6	3	47	1445.2	1,317	553	595	145	395	38	32	5,932	52	8.69	2.46	3.53	0.90	23.5	6.7	1.18	.296	3.70	8.20
6	Astros	3.57	2015	162	.531	86	76	162	1,280	5	3	39	1441.0	1,308	572	618	148	423	43	17	5,965	61	7.99	2.64	3.03	0.92	21.5	7.1	1.20	.285	3.86	8.17
7	Nationals	3.62	2015	162	.512	83	79	162	1,342	4	3	41	1434.2	1,366	577	635	145	364	55	37	5,975	39	8.42	2.28	3.69	0.91	22.5	6.1	1.21	.300	3.98	8.57
8	Indians	3.67	2015	161	.503	81	80	161	1,407	11	1	38	1432.2	1,274	584	640	161	425	48	27	5,904	48	8.84	2.67	3.31	1.01	23.8	7.2	1.19	.288	4.02	8.00
9	Giants	3.72	2015	162	.519	84	78	162	1,165	7	4	41	1444.1	1,344	597	627	155	431	50	28	6,009	40	7.26	2.69	2.70	0.97	19.4	7.2	1.23	.283	3.91	8.37
10	Royals	3.73	2015	162	.586	95	67	162	1,160	2	1	56	1452.0	1,372	601	641	155	489	52	10	6,112	62	7.19	3.03	2.37	0.96	19.0	8.0	1.28	.286	3.97	8.50
11	Rays	3.74	2015	162	.494	80	82	162	1,355	1	1	60	1453.1	1,314	604	642	175	477	46	23	6,069	81	8.39	2.95	2.84	1.08	22.3	7.9	1.23	.284	3.98	8.14
12	Blue Jays	3.80	2015	162	.574	93	69	162	1,117	7	2	34	1441.0	1,353	609	670	173	397	59	20	5,984	62	6.98	2.48	2.81	1.08	18.7	6.6	1.21	.278	4.18	8.45
13	Angels	3.94	2015	162	.525	85	77	162	1,221	2	2	46	1440.2	1,355	630	675	166	466	71	45	6,096	61	7.63	2.91	2.62	1.04	20.0	7.6	1.26	.285	4.22	8.46
14	White Sox	3.98	2015	162	.469	76	86	162	1,359	7	4	37	1452.2	1,443	643	701	162	474	62	34	6,181	61	8.42	2.94	2.87	1.00	22.0	7.7	1.32	.311	4.34	8.94
15	Marlins	4.02	2015	162	.438	71	91	162	1,152	0	0	35	1427.0	1,374	638	678	141	508	52	25	6,050	53	7.27	3.20	2.27	0.89	19.0	8.4	1.32	.294	4.28	8.67
16	Yankees	4.03	2015	162	.537	87	75	162	1,370	3	0	48	1457.2	1,416	652	698	182	474	56	16	6,191	78	8.46	2.93	2.89	1.12	22.1	7.7	1.30	.300	4.31	8.74
17	Diamondbacks	4.04	2015	162	.488	79	83	162	1,215	1	1	44	1466.2	1,450	659	713	182	500	48	45	6,257	51	7.46	3.07	2.43	1.12	19.4	8.0	1.33	.294	4.38	8.90
18	Orioles	4.05	2015	162	.500	81	81	162	1,233	0	0	43	1434.2	1,406	646	693	174	483	54	27	6,085	46	7.73	3.03	2.55	1.09	20.3	7.9	1.32	.298	4.35	8.82
19	Twins	4.07	2015	162	.512	83	79	162	1,046	2	0	45	1443.0	1,506	653	700	163	413	41	34	6,139	54	6.52	2.58	2.53	1.02	17.0	6.7	1.33	.300	4.37	9.39
20	Padres	4.09	2015	162	.457	74	88	162	1,393	1	0	41	1440.1	1,371	655	731	171	516	54	35	6,093	54	8.70	3.22	2.70	1.07	22.9	8.5	1.31	.303	4.57	8.57
21	Athletics	4.14	2015	162	.420	68	94	162	1,179	5	3	28	1444.2	1,402	664	729	172	474	47	19	6,128	62	7.34	2.95	2.49	1.07	19.2	7.7	1.30	.289	4.54	8.73
22	Mariners	4.16	2015	162	.469	76	86	162	1,283	6	5	45	1463.0	1,430	677	726	181	491	70	41	6,223	72	7.89	3.02	2.61	1.11	20.6	7.9	1.31	.298	4.47	8.80
23	Rangers	4.24	2015	162	.543	88	74	162	1,095	5	3	45	1442.2	1,459	680	733	171	508	63	29	6,215	51	6.83	3.17	2.16	1.07	17.6	8.2	1.36	.294	4.57	9.10
24	Brewers	4.28	2015	162	.420	68	94	162	1,260	1	0	40	1435.0	1,432	682	737	176	517	55	36	6,148	71	7.90	3.24	2.44	1.10	20.5	8.4	1.36	.303	4.62	8.98
25	Red Sox	4.31	2015	162	.481	78	84	162	1,218	3	1	40	1448.1	1,486	694	753	178	478	62	17	6,225	79	7.57	2.97	2.55	1.11	19.6	7.7	1.36	.305	4.68	9.23