Video surveillance systems have a huge market, as indicated by the number of installed cameras, particularly for low-power systems. In this paper, we propose a low-power quadtree video encoder for video surveillance systems. It features a low-complexity motion estimation algorithm, an application-specific ME-MC processor, a dedicated quadtree encoder engine and a processor control-based clock-gating technique. A chip capable of encoding 30 fps VGA (640480) at 80 MHz is fabricated using 0.18 µm CMOS technology. A total of 153 K gates with 558 kbits SRAM have been integrated into a 5.0 mm3.5 mm die. The power consumption is 40.87 mW at 80 MHz for VGA at 30 fps and 1.97 mW at 3.3 MHz for QCIF at 15 fps.