Worst-case execution time (WCET) analysis has reached a high level of precision in the analysis of sequential programs executing on single-cores. In this paper we extend a state-of-the-art WCET analysis technique to compute tight WCETs estimates of parallel applications running on multicores. The proposed technique is termed integrated because it considers jointly the sequential code regions running on the cores and the communications between them. This allows to capture the hardware effects across code regions assigned to the same core, which significantly improves analysis precision. We demonstrate that our analysis produces tighter execution time bounds than classical techniques which first determine the WCET of sequential code regions and then compute the global response time by integrating communication costs. Comparison is done on two embedded control applications, where the gain is of 21% on average.