In this paper shape and size optimization of truss structures subjected to frequency constraints is addressed utilizing a newly developed multi-agent meta-heuristic algorithm called Tug of War Optimization (TWO). The algorithm considers each candidate solution as a team participating in a series of rope pulling competitions. Frequency constraint structural optimization corresponds to highly non-linear, discontinuous, and non-convex search spaces including several local optima. Such problems call for properly balanced competent optimization algorithms. Here, viability of TWO is demonstrated using four numerical examples.