Mechanism of tear of unfilled and carbon black filled carboxylated nitrile rubber (XNBR) having metallocarboxylate crosslinks, sulfur-sulfur crosslinks and mixed type crosslinking systems has been studied by Scanning Electron Microscope. Tear proceeds through stick-slip process in the case of gum mixes. The number of tear lines is more in the sulfur crosslinked system, resulting in poor tear strength. Addition of reinforcing carbon black changes the mechanism of tear. The sulfur crosslinked system shows knotty tear, while introduction of ionic crosslinks results in smooth tear presumably due to the large tip diameter reaching the edge of the specimen.