This article introduces several mathematical formulations for the joint order picking problem (JOPP) in low-level picker-to-part warehousing systems. In order to represent real warehousing environments, the proposed models minimize performance measures such as travel distance, travel time and tardiness, considering multi-block warehouses, due dates, and multiple pickers. The number of constraints and decision variables required for each proposed model is calculated, demonstrating the complexity of solving medium and long-sized problems in reasonable computing time using exact methods, so it is still recommendable to solve these JOPP using metaheuristics. The proposed models can be followed as a reference for new solution methods that yield efficient and fast solutions. © 2020, Institute of Advanced Engineering and Science. All rights reserved.