Assembly line balancing problem (ALBP) is one of the well-known NP-hard layout planning problems for mass production systems. Many exact solution approaches have been developed, including 0–1 integer programming model, branch and bound algorithm, dynamic programming model, etc.; however, all optimal approaches are computationally inefficient in solving large-scale problems, which makes heuristic approaches a necessity in practice. In this paper we propose a new efficient heuristic, based on a recent bidirectional approach and the famous critical path method (CPM) widely used in project management, to resolve the issue of task assignment for ALBP. An example is given for illustration, and numerical results of sample problems selected from the literature are also given to show the effectiveness of the proposed heuristic.