This paper presents a new enhanced version of the social engineering optimizer (SEO), named as MSEO, for size and shape optimization of truss structures considering dynamic constraints.The proposed MSEO introduces a concept drawn from artificial ecosystem-based optimization (AEO), known as decomposition operator, into the standard SEO to improve the exploitation capability.To validate the proposed algorithm thirty functions extracted from the CEC2014 database and six benchmark truss optimization problems with dynamic constraints are analyzed.Numerical results and comparison to other state-of-the-art metaheuristics optimization methods reveal the effectiveness of the proposed method.