Results from optical CCD photometric observations of 13 pre-main-sequence stars collected during the period from February 2007 to November 2020 are presented. These stars are located in the association Cepheus OB3, in the field of the young star V733 Cephei. Photometric observations, especially concerning the long-term variability of the stars, are missing in the literature. We present the first long-term V(RI)c monitoring for them, that cover 13 years. Results from our study indicate that all of the investigated stars manifest strong photometric variability. The presented paper is a part of our program for the photometric study of pre-main-sequence stars located in active star-forming regions.