Millions of people around the world are affected by mental illness, yet a substantive portion of individuals with mental illness do not regularly seek help from medical professionals or utilize mental health services. Help-seeking involves an individual's communicative intention and behaviors to solicit advice and/or treatment and thus is essentially a communicative process. This manuscript reports a longitudinal study that examined predictors and outcomes of help-seeking in mental illness contexts. Three-wave data from 223 participants clinically diagnosed with one or more mental illness conditions were collected and analyzed. Results indicated that expected outcomes of help-seeking from counselors were significantly associated with participants' communication efficacy and target efficacy at Wave 1, which subsequently influenced motivation to seek help and actual help-seeking behaviors at Wave 2. Actual help-seeking behaviors predicted post-traumatic growth and cognitive reappraisal at Wave 3. Importantly, communication efficacy and target efficacy interacted in their effects on help-seeking motivation and behaviors. Theoretical implications for help-seeking communication processes and practical implications for mental health help-seeking are discussed.