Although exposure is an effective treatment for anxiety disorders, its efficacy is limited, and efforts are being made to enhance its overall effectiveness. This dissertation evaluates one potential method of optimizing extinction learning and exposure therapy: increasing positive affect during extinction. The effect of positive affect on learning is discussed in regards to various components of learning, including attention, encoding, rehearsal, consolidation, retrieval, and stimulus appraisal. These effects are then discussed specifically with regard to extinction learning and exposure therapy. Study 1 evaluated whether positive affect is associated with lower rates of reacquisition, or, an increase in fear following re-pairings of the conditional stimulus (CS+) and unconditional stimulus (US; e.g., electric shock) after extinction. Results showed that higher positive affect before and after extinction was associated with less CS+ fear during reacquisition as measured by skin conductance arousal and US expectancy. Study 2 used a mood induction to assess its effects on spontaneous recovery, long-term extinction learning, and reacquisition. This study found null results of mood induction on fear. Study 3 evaluated the effects of mood induction on generalization of extinction learning. The results showed that positive mood induction before extinction resulted in less self-report fear of a novel generalization stimulus at test. The results of all three studies are discussed with relevance to exposure therapy.