The Seattle Mariners had the worst winning percentage by a team in 1978, winning 35.0 percent of the time.

	TEAM	W%	SEASON	W	L	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	Mariners	.350	1978	56	104	160	5,358	614	1,327	229	37	97	571	522	22	702	123	47	6,023	1,921	363	68	53	25	112	.248	.314	.359	.673
2	Blue Jays	.366	1978	59	102	161	5,430	590	1,358	217	39	98	551	448	23	645	28	52	6,015	1,947	354	77	37	23	124	.250	.308	.359	.667
3	Mets	.407	1978	66	96	162	5,433	607	1,332	227	47	86	561	549	24	829	100	77	6,132	1,911	360	71	55	59	126	.245	.314	.352	.666
4	Braves	.426	1978	69	93	162	5,381	600	1,313	191	39	123	558	550	27	874	90	65	6,066	1,951	353	61	47	53	140	.244	.315	.363	.677
5	Cardinals	.426	1978	69	93	162	5,415	600	1,351	263	44	79	568	420	22	713	97	42	5,965	1,939	386	55	53	55	131	.249	.303	.358	.661
6	Athletics	.426	1978	69	93	162	5,321	532	1,304	200	31	100	492	433	25	800	144	117	5,914	1,866	331	108	27	33	106	.245	.303	.351	.654
7	Indians	.434	1978	69	90	159	5,365	639	1,400	223	45	106	596	488	26	698	64	63	6,011	2,031	374	92	40	31	124	.261	.323	.379	.702
8	White Sox	.441	1978	71	90	161	5,393	634	1,423	221	41	106	595	409	33	625	83	68	5,955	2,044	368	63	57	20	122	.264	.317	.379	.696
9	Twins	.451	1978	73	89	162	5,522	666	1,472	259	47	82	621	604	33	684	99	56	6,323	2,071	388	109	55	43	139	.267	.339	.375	.714
10	Astros	.457	1978	74	88	162	5,458	605	1,408	231	45	70	557	434	22	743	178	59	6,034	1,939	346	76	44	67	134	.258	.313	.355	.668
11	Expos	.469	1978	76	86	162	5,530	633	1,404	269	31	121	589	396	35	881	80	42	6,063	2,098	421	62	40	62	126	.254	.306	.379	.685
12	Cubs	.488	1978	79	83	162	5,532	664	1,461	224	48	72	612	562	21	746	110	58	6,258	1,997	344	84	59	61	125	.264	.331	.361	.692
13	Padres	.519	1978	84	78	162	5,360	591	1,349	208	42	75	542	536	32	848	152	70	6,081	1,866	325	114	39	87	81	.252	.321	.348	.669
14	Tigers	.531	1978	86	76	162	5,601	714	1,520	218	34	129	666	563	31	695	90	38	6,299	2,193	381	57	47	32	145	.271	.339	.392	.730
15	Angels	.537	1978	87	75	162	5,472	691	1,417	226	28	108	646	539	67	682	86	69	6,206	2,023	362	72	56	38	135	.259	.330	.370	.700
16	Rangers	.537	1978	87	75	162	5,347	692	1,353	216	36	132	650	624	32	779	196	91	6,141	2,037	384	83	55	45	115	.253	.332	.381	.713
17	Pirates	.547	1978	88	73	161	5,406	684	1,390	239	54	115	631	480	42	874	213	90	6,038	2,082	408	64	46	89	95	.257	.320	.385	.705
18	Giants	.549	1978	89	73	162	5,364	613	1,331	240	41	117	576	554	17	814	87	54	6,102	2,004	398	127	40	75	104	.248	.318	.374	.692
19	Phillies	.556	1978	90	72	162	5,448	708	1,404	248	32	133	661	552	42	866	152	58	6,152	2,115	413	61	49	88	93	.258	.328	.388	.716
20	Orioles	.559	1978	90	71	161	5,422	659	1,397	248	19	154	612	552	22	864	75	61	6,079	2,145	421	41	42	34	136	.258	.326	.396	.722
21	Royals	.568	1978	92	70	162	5,474	743	1,469	305	59	98	695	498	30	644	216	84	6,129	2,186	462	55	72	44	95	.268	.329	.399	.728
22	Reds	.571	1978	92	69	161	5,392	710	1,378	270	32	136	669	636	26	899	137	58	6,192	2,120	438	84	54	72	112	.256	.334	.393	.727
23	Brewers	.574	1978	93	69	162	5,536	804	1,530	265	38	173	762	520	32	805	95	53	6,227	2,390	476	89	50	38	94	.276	.339	.432	.771
24	Dodgers	.586	1978	95	67	162	5,437	727	1,435	251	27	149	686	610	20	818	137	52	6,225	2,187	427	111	47	76	101	.264	.338	.402	.740
25	Red Sox	.607	1978	99	64	163	5,587	796	1,493	270	46	172	738	582	24	835	74	51	6,316	2,371	488	65	58	43	135	.267	.336	.424	.760