Under deposit corrosion (UDC) has been identified as a phenomenon responsible for many operation failures, representing a threat to pipelines integrity and seawater injection systems. Despite the recent efforts to define the effects of deposits on corrosion of steel surfaces and their inhibition, the influence of microorganisms in these deposited environments have not been largely addressed. Understanding the effect of microbial activity on UDC is important because microbial cells thrive in deposits resulting in an adverse combination of microbiologically influenced corrosion (MIC) and UDC. Additionally, UDC mitigation constitutes a challenging topic since solid particles can decrease the availability of inhibitor molecules to protect the underlying steel against corrosion. Biofilms comprise a complex array of molecules and microorganisms that can act as organic deposits compromising the performance of corrosion inhibitors. Therefore, is important to evaluate the corrosion inhibitor efficiency in the presence of biofilm-deposits formed on steels surfaces. This document reviews the literature on UDC-MIC mechanisms, testing methods and prospects in the understanding and inhibition of these complex phenomena.