4 players were 27 years old. The first three are John Stockton in 1989-90, Magic Johnson in 1986-87 and James Harden in 2016-17.

the oldest player to lead the league in assists in nba in single season

NAME	AGE	APG	SEASON	TM	GP	MPG	PPG	RPG	SPG	BPG	TPG	FGM	FGA	FG%	3PM	3PA	3P%	FTM	FTA	FT%	MIN	PTS	REB	AST	STL	BLK	TOV	PF	+/-
John Stockton	27	14.5	1989-90	UTA	78	37.4	17.2	2.6	2.7	0.2	3.5	6.1	11.8	51.4	0.6	1.4	41.6	4.5	5.5	81.9	2,915	1,345	206	1,134	207	18	272	233
John Stockton	28	14.2	1990-91	UTA	82	37.8	17.2	2.9	2.9	0.2	3.6	6.0	11.9	50.7	0.7	2.0	34.5	4.4	5.3	83.6	3,103	1,413	237	1,164	234	16	298	233
Isiah Thomas	23	13.9	1984-85	DET	81	38.1	21.2	4.5	2.3	0.3	3.7	8.0	17.4	45.8	0.4	1.4	25.7	4.9	6.1	80.9	3,089	1,720	361	1,123	187	25	302	288
John Stockton	25	13.8	1987-88	UTA	82	34.7	14.7	2.9	3.0	0.2	3.2	5.5	9.6	57.4	0.3	0.8	35.8	3.3	4.0	84.0	2,842	1,204	237	1,128	242	16	262	247
John Stockton	29	13.7	1991-92	UTA	82	36.6	15.8	3.3	3.0	0.3	3.5	5.5	11.5	48.2	1.0	2.5	40.7	3.8	4.5	84.2	3,002	1,297	270	1,126	244	22	286	234
John Stockton	26	13.6	1988-89	UTA	82	38.7	17.1	3.0	3.2	0.2	3.8	6.1	11.3	53.8	0.2	0.8	24.2	4.8	5.5	86.3	3,171	1,400	248	1,118	263	14	308	241
Kevin Porter	28	13.4	1978-79	DET	82	37.4	15.4	2.5	1.9	0.1	4.1	6.5	13.5	48.1				2.3	3.2	72.2	3,064	1,260	209	1,099	158	5	337	302
Magic Johnson	24	13.1	1983-84	LAL	67	38.3	17.6	7.3	2.2	0.7	4.6	6.6	11.6	56.5	0.1	0.4	20.7	4.3	5.3	81.0	2,567	1,178	491	875	150	49	306	169
Magic Johnson	29	12.8	1988-89	LAL	77	37.5	22.5	7.9	1.8	0.3	4.1	7.5	14.8	50.9	0.8	2.4	31.4	6.7	7.3	91.1	2,886	1,730	607	988	138	22	312	172
Magic Johnson	26	12.6	1985-86	LAL	72	35.8	18.8	5.9	1.6	0.2	3.8	6.7	12.8	52.6	0.1	0.6	23.3	5.3	6.0	87.1	2,578	1,354	426	907	113	16	273	133
John Stockton	31	12.6	1993-94	UTA	82	36.2	15.1	3.1	2.4	0.3	3.2	5.6	10.6	52.8	0.6	1.8	32.2	3.3	4.1	80.5	2,969	1,236	258	1,031	199	22	266	236
Magic Johnson	25	12.6	1984-85	LAL	77	36.1	18.3	6.2	1.5	0.3	4.0	6.5	11.7	56.1	0.1	0.5	18.9	5.1	6.0	84.3	2,781	1,406	476	968	113	25	305	155
Magic Johnson	31	12.5	1990-91	LAL	79	37.1	19.4	7.0	1.3	0.2	4.0	5.9	12.4	47.7	1.0	3.2	32.0	6.6	7.3	90.6	2,933	1,531	551	989	102	17	314	150
John Stockton	32	12.3	1994-95	UTA	82	35.0	14.7	3.1	2.4	0.3	3.3	5.2	9.6	54.2	1.2	2.8	44.9	3.0	3.7	80.4	2,867	1,206	251	1,011	194	22	267	215
Kevin Johnson	22	12.2	1988-89	PHX	81	39.2	20.4	4.2	1.7	0.3	4.0	7.0	13.9	50.5	0.0	0.3	9.1	6.3	7.1	88.2	3,179	1,650	340	991	135	24	322	226
Magic Johnson	27	12.2	1986-87	LAL	80	36.3	23.9	6.3	1.7	0.5	3.8	8.5	16.4	52.2	0.1	0.5	20.5	6.7	7.9	84.8	2,904	1,909	504	977	138	36	300	168
John Stockton	30	12.0	1992-93	UTA	82	34.9	15.1	2.9	2.4	0.3	3.2	5.3	11.0	48.6	0.9	2.3	38.5	3.6	4.5	79.8	2,863	1,239	237	987	199	21	266	224
Magic Johnson	28	11.9	1987-88	LAL	72	36.6	19.6	6.2	1.6	0.2	3.7	6.8	13.8	49.2	0.2	0.8	19.6	5.8	6.8	85.3	2,637	1,408	449	858	114	13	269	147
Russell Westbrook	32	11.7	2020-21	WAS	65	36.4	22.2	11.5	1.4	0.4	4.8	8.4	19.0	43.9	1.3	4.2	31.5	4.2	6.4	65.6	2,369	1,445	750	763	89	23	312	190	-87
Rajon Rondo	25	11.7	2011-12	BOS	53	36.9	11.9	4.8	1.8	0.1	3.6	4.8	10.8	44.8	0.2	0.8	23.8	2.0	3.4	59.7	1,957	630	257	620	95	3	193	99	+196
Rajon Rondo	29	11.7	2015-16	SAC	72	35.2	11.9	6.0	2.0	0.1	3.9	4.9	10.9	45.4	0.9	2.4	36.5	1.2	2.1	58.0	2,537	859	435	839	141	10	278	175	-149
Steve Nash	32	11.6	2006-07	PHX	76	35.3	18.6	3.5	0.8	0.1	3.8	6.8	12.8	53.2	2.1	4.5	45.5	2.9	3.3	89.9	2,682	1,412	269	884	57	6	287	117	+609
Chris Paul	22	11.6	2007-08	NOH	80	37.6	21.1	4.0	2.7	0.1	2.5	7.9	16.1	48.8	1.2	3.1	36.9	4.2	4.9	85.1	3,006	1,684	321	925	217	4	201	185	+479
Magic Johnson	30	11.5	1989-90	LAL	79	37.2	22.3	6.6	1.7	0.4	3.7	6.9	14.4	48.0	1.3	3.5	38.4	7.2	8.1	89.0	2,937	1,765	522	907	132	34	289	167
Steve Nash	30	11.5	2004-05	PHX	75	34.3	15.5	3.3	1.0	0.1	3.3	5.7	11.4	50.2	1.3	2.9	43.1	2.8	3.2	88.7	2,573	1,165	249	861	74	6	245	136	+664