Reverse-transcriptase quantitative PCR (RT-qPCR) is a widely used method for quantifying microRNAs (miRNAs) in cells and tissues. However, the quantification of miRNAs in the circulation presents specific challenges. Here, we describe an optimized protocol using a small amount of input material to assess serum sample quality and quantify levels of a panel of up to 20 miRNAs. This is achieved by multiplexing Taqman miRNA stem-loop primers in the reverse transcription step. An additional multiplexed pre-amplification step is used to increase the sensitivity of the final quantification step, which is carried out using standard Taqman qPCR methodology.