The influences of debonding rate and temperature on the peel behavior of polyacrylic block copolymer/tackifier system were investigated. Poly(methyl methacrylate)-block-poly(n-butyl acrylate)-block-poly(methyl methacrylate) triblock copolymer (MAM) with hard block contents of 23 (MAM-23) and 16wt.% (MAM-16) and a 1/1 blend with a diblock copolymer (MA) consisting of the same components (MAM-23/MA, total hard block content of 15wt.%) were used as the base polymer. A special rosin ester was used as a tackifier at various contents in the block copolymer/tackifier system. The peeling process at the probe/adhesive interface during probe tack testing was observed using a high-speed microscope at 23 degrees C with debonding rate of 10mm/s. Three different peeling mechanisms were observed. Type A, where peeling progressed linearly from the edge to the center of the probe without cavitation (MAM-23). Type B, where peeling progressed linearly from the edge to the center of the probe with cavitation (MAM-16). Type C, where cavitation occurred over the entire adhesive layer, and peeling initiation was delayed (MAM-23/MA). The peel behavior of MAM-23 changed from Type A to Type B with a decrease of the debonding rate (1mm/s) or increase of the temperature (40 degrees C). In contrast, there was no change for MAM-16 and MAM-23/MA. Cavity formation in an adhesive layer restrains peeling; therefore, it is desirable for improvement of the adhesion strength. The tack properties increased with the tackifier content, and the formation of cavitation was less than that for the systems without the tackifier.