There are two terminal precincts at Perth Airport that are separated by a short, 15-minute drive: the T1/T2 precinct and the T3/T4 precinct.

If you need to transfer between T1/T2 and T3/T4, taxi and rideshare services are available on the respective terminal forecourts.

The terminal transfer bus is also available and operates every 40 minutes.

Departing from: 

T3/T4am	T2 am	T3/T4 pm	T2 pm
00:20	00:35	12:20	12:35
01:00	01:15	13:00	13:15
01:40	01:55	13:40	13:55
02:20	02:35	14:20	14:35
03:00	03:15	15:00	15:15
03:40	03:55	15:40	15:55
04:20	04:35	16:20	16:35
05:00	05:15	17:00	17:15
05:40	05:55	17:40	17:55
06:20	06:35	18:20	18:35
07:00	07:15	19:00	19:15
07:40	07:55	19:40	19:55
08:20	08:35	20:20	20:35
09:00	09:15	21:00	21:15
09:40	09:55	21:40	21:55
10:20	10:35	22:20	22:35
11:00	11:15	23:00	23:15
11:40	11:55	23:40	23:55

Airport maps are available here.