Searching for olfactory targets with mobile robots has received much attention in the recent years due to its applications in chemical leak detection, environmental monitoring, pollution monitoring, inspection of landfills, and search and rescue operations. This thesis aims to address the problem of searching for olfactory targets with a group of mobile robots. A group of robots with on-board sensors can actually form a mobile sensor network, so they can cover larger area in a shorter time and they show better performance in several scenarios in comparison to a single robot. Two types of robotic groups are considered in this thesis; “multi-robot systems” and “swarm robotic systems.” For each of these systems a certain objective is defined to address several challenges in robotic olfactory search. “Olfactory search and exploration with multiple robots in structured unknown environments” and “swarm robotics olfactory search in unstructured unknown environments” are the two defined objectives of this thesis. In both objectives, the problem of “odor plume finding” that is the first step to localize odor sources is considered as the main problem.