Abstract: A tamper-proof two-piece cover for container spout caps having a pair of collars which are detachably secured by fasteners about the spout of the container and a top which when latched to the collars completely encloses the container cap and the collar securing fasteners. Each collar has a pair of threaded tubular members disposed at its periphery. A pair of bolts are received in the threaded tubular members to secure the collars about a container spout. A top is hinged to one collar and rotatable about the hinge to a position where the top completely encloses the container cap and the bolts. A latch secures the top to one of the collars so that the top may be locked in place over the cap. The collar members may be configured to fit standard sized tank spouts and the inter-collar spacing is further adjustable to fit non-standard sized tank spouts by simply varying the degree to which the retaining bolts are screwed into the threaded tubular members.