This study investigates how second language (L2) fluency is influenced by two factors: Pre-task planning and content familiarity. Planning was adopted as a between-participant variable, combined with content familiarity as a within-participant variable, in a 2 × 2 split-plot factorial design. Nineteen measures of fluency phenomena, constituting eight categories, were used. Both planning and content familiarity were found to enhance fluency, but the positive effects of planning were stronger and noticeable on a wider range of measures. The availability of planning time also helped to compensate for lack of content familiarity. Implications for pedagogy and L2 fluency measurement are discussed.