Diastereoselective [2 + 2] photocycloaddition of chiral cyclohexenone 1 with cyclopentene was conducted using a continuous microflow reactor. This reaction led to photoadducts 2 and 3 in a shorter reaction time and with a higher diastereoselectiviy than the corresponding reaction in a batch reactor. The effect of temperatures on the selectivities of both reaction systems is also discussed.