Congestion control is a challenging task in Wireless Sensor Networks (WSNs) as it upset Packet delivery ratio (PDR), Latency, energy consumption, quality of output data retrieved at Base station (BS)/sink node. Node buffer overflow, link failure between nodes, channel contention, Interference, packet collision, high transmission rate at the source nodes are some of the reasons for Congestion in WSNs. With the development of WSN based on the Internet of Things (IoT), the importance of Congestion control increases and the need to provide more efficient strategies to deal with this problem is strongly felt. Optimization is always a challenging process in any network. This paper provides brief overview of the congestion control algorithms used in WSNs.