Multi-machine scheduling has been one of the best-known and practical problems in the last decade and its applications are constantly increasing. This study addresses an unrelated parallel machine scheduling problem with family setups and soft time windows, in which machine eligibility and precedence constraints are considered. The objective is to minimize the total of weighted early and tardy costs. The problem is investigated for different sizes of jobs, families and machines. Two different metaheuristic algorithms, a simulated annealing (SA) and an artificial immune system (AIS) are presented. Two strategies called repair and penalty are proposed to implement predecessor constraints. Some computational experiments are performed and one-way analysis of variance (ANOVA) is conducted to compare the performance of the proposed metaheuristics and evaluate the designed combinations in terms of objective values and computational (CPU) times. Results demonstrate that SA with repair strategy generally outperforms other proposed methods.