Level of contributors\u27 activity around an Open Source Software (OSS) project is one of the key factors in terms of its survival and success. There are several factors that affect a developer\u27s decision to join an OSS project, yet little research examined the influence of third-party assessments on a developer\u27s intention to join a project. Drawing on signaling theory, this manuscript explores how third-party assessment can influence a developers\u27 decision to join an OSS project. In order to test it, vignette survey study was conducted manipulating reputation, development experience, and a number of current OSS projects of existing developers in the OSS project. The findings suggest that all three signals have a positive influence on developer\u27s decision to join the OSS project. This suggests that projects seeking to expand the number of contributing developers should consider offering information about its star developers