In Wireless Sensor Networks (WSNs), congestion can cause a number of problems including packet loss, lower throughput and poor energy efficiency. These problems can potentially result in reduced deployment lifetime and under-performing applications. This has led to several proposals for congestion control (CC) mechanisms for sensor networks. Furthermore, the WSN research community has made significant efforts towards power saving MAC protocols with Radio Duty Cycling (RDC). However, careful study of previous work reveals that RDC schemes are often neglected during the design and evaluation of CC algorithms. In this context, this paper contributes a new CC scheme for Duty Cycle and IPv6 over Low power Wireless Personal Area Networks 6LoWPAN sensor Networks — DCCC6. DCCC6 detects the presence of duty cycling and adjust its operation accordingly. We evaluate DCCC6 both with simulations and on a testbed with multi node topologies. The experimental results have shown that DCCC6 achieved higher goodput and lower packet loss than previous works. Moreover, simulations show that DCCC6 maintained low energy consumption, average delay times and achieved a high degree of fairness.