Social media is an increasingly important source for tourists seeking information about their intending holidays. Tourists obtain travel related information by interacting with their social networks. However, social media users’ collaborative search behavior is an under-studied area. This paper investigates collaborative search behavior of mobile social media users when they plan for a group trip. We surveyed sixty-three (63) Australian participants. Findings show that tourists collaborated on social media for a range of trip planning activities, such as searching, gathering, obtaining, sharing and validating information at different stages of the trip planning process. Notable findings include 92.10% of participants used Facebook messenger for collaborations, and the majority (62.96%) searched on social media for information about attractions to see at their destination; also, 73.80% used social media to gather information related to their travel at the beginning of their planning process and 41% used social media at the end of planning process to validate information for their travel decision-making. About 42.86% changed their minds as a result of social media interactions.