Introduction Recent controlled trials have assessed the efficacy of phospodiesterase-5 (PDE-5) inhibitors in secondary Raynaud's phenomenon (RP). However, the conclusions are conflicting, and whether these drugs are effective remains unclear. The objective of this meta-analysis was to determine the efficacy of PDE-5 inhibitors on Raynaud's Condition Score (RCS) and frequency and duration of attacks. Methods A systematic review of articles was performed (sources included Medline, Embase, Web of Science, the Cochrane Central Register of Controlled Trials). Only double-blind, randomised controlled trials (RCTs) were included. Studies were selected independently by two authors using predefined data fields, including study quality indicators. Results Six RCTs were included (one with sildenafil, one with modified-release sildenafil, three with tadalafil and one with vardenafil). PDE-5 inhibitors significantly decreased mean RCS by −0.46 (−0.74 to −0.17) (p=0.002), the daily frequency of ischaemic attacks by −0.49 (−0.71 to −0.28) (p<0.0001), and daily duration of RP attacks by −14.62 (−20.25 to −9.00) min (p<0.0001). Conclusions PDE-5 inhibitors appear to have significant but moderate efficacy in secondary RP. A further large RCT is needed.