Researchers working in the work-family conflict (WFC) literature have a long history of focusing on how conflict between the work and family domains influences employees and their experiences inside and outside of work (Eby et al., 2005). However, missing from the literature is how a coworker’s WFC, specifically in the direction of family interfering with work (FIW), can go beyond influencing the person experiencing the FIW to impact other people in the work environment, such as other employees. The present study used a weekly diary study and multilevel modeling to investigate how fluctuations in coworker FIW are related to fluctuations in a focal employee’s helping behavior, as well as how engaging in that helping behavior may influence the relationship quality between coworkers and focal employees and may lead to increased role overload, work interfering with family (WIF), and need for recovery for the focal employee. The study also tested whether having higher levels of prosocial motivation moderates the relationship between coworker FIW and focal employee helping behavior. Results from the multilevel analyses indicated coworker FIW was not related to whether or not a focal employee will engage in helping behavior, and prosocial motivation levels did not moderate this relationship between coworker FIW and helping behavior. However, engaging in helping behavior was related to increased focal employee role overload and relationship quality, but not to WIF or need for recovery. Implications and limitations of these findings for the WFC literature are discussed.