A naturalistic study was conducted to investigate the influence of optimism on the regulation of daily sad mood. 161 undergraduate students (n = 116, 72 % female) with a mean age of 20.54 years (SD = 5.04) participated. The sample majority was Caucasian (n = 149, 92.5 %). At baseline participants completed questionnaires that included the Life Orientation Test-Revised (LOT-R) followed by a 7 day online mood, cognition and emotion regulation diary. Correlational analyses revealed LOT-R was associated with active repair, increased use of both adaptive and maladaptive repair strategies, reduced negative cognitions and greater perceived effectiveness, but was unrelated to sadness duration. Multi-level modeling revealed LOT-R did not interact with adaptive and maladaptive mood regulation strategies to predict ability to implement strategies, however perceived effectiveness was less tied to strategy type for those higher on LOT-R. Active repair and perceptions of control over emotions may contribute to enhanced affective functioning associated with optimism.