Objective The available literature points to the potential therapeutic benefits of alliance strengthening during treatment. Both supportive and expressive techniques have been suggested to be associated with strengthening of the alliance. The present study investigates whether patients may show different effects of supportive vs. expressive techniques in improving alliance as a function of their pretreatment insight levels. Method Fifty-five patients were randomly assigned to either supportive treatment (ST) or supportive-expressive treatment (SET), as part of a larger randomized controlled trial. Clinical interviews were administered at pretreatment to evaluate the patients' level of insight. The working alliance was measured after each of the 16 sessions. A multilevel model, including a 3-way interaction of pretreatment insight by treatment condition (ST vs. SET) by time, was used to predict alliance strengthening. Results The findings suggest that, for individuals receiving ST, those with higher levels of insight show greater alliance strengthening. For individuals receiving SET, those with lower levels of insight show greater alliance strengthening. Conclusion The current study suggests that one size may not fit all and, whereas some individuals may benefit more from ST to achieve alliance strengthening, others may benefit more from SET.