We obtained multi-colour light curves of the overcontact binary system HH Boo and analysed the orbital period variation of the system. Our analysis tentatively indicates either mass transfer from the secondary to the primary or mass loss from the system at a rate of -5.04 x 10(-7) M-circle dot per year. Through a combined analysis of the published radial velocity curve and light curves, we determined an inclination (i) of 69 degrees.71 +/- 0 degrees.16 and a semi-major axis (a) of 2.246 +/- 0.064 R-circle dot for HH Boo. The masses of the primary and secondary components were found to be 0.92 +/- 0.08 M-circle dot and 0.58 +/- 0.06 M-circle dot, respectively. The radius determined for the primary was 0.98 +/- 0.03 R-circle dot, while that determined for the secondary was 0.80 +/- 0.02 R-circle dot. We demonstrated that HH Boo is most likely a member of the A-type subclass of W UMa binaries. Published by Elsevier B.V.