Karimian had replaced Croatian coach Miso Krsticevic on July 1.
In his first match as interim coach, Shahin lost to 10-man Persepolis 1-0 in Tehran and the team suffered a heavy 5-1 loss against Zob Ahan on Friday.
Shahin Bushehr is rooted to the bottom of the Iran Professional league (IPL) table on 17 points.
The Bushehr-based club has announced that it will introduce the new coach within one day.