Upper limb function is one of the most affected domains in people with multiple sclerosis (PwMS), as self-reported by 50% of patients. Heterogeneous results have been found about the correlation between objective and subjective upper limb function. The aim of the present study is to perform a systematic review and meta-analysis of studies presenting data on the strength of association between the gold standard for 9-Hole Peg Test scores and Patient-Reported Outcome Measures (PROMs) of manual ability. Primary research studies including assessments of 9-Hole Peg Test scores and Patient-Reported Outcome Measures were searched in Scopus, Web of Science, and PubMed. Meta analytical calculations were performed using a random-effects model. We retrieved n = 27 studies including n = 75 distinct effect sizes (N of subjects = 3263). The central tendency analysis showed a strong correlation between 9-HPT scores and PROMs (r = 0.51, 95% CI [0.44, 0.58]). Moderator analysis showed the effect size to be significantly larger in studies with a mean or median EDSS level indicating severe disability. The publication bias hypothesis was not supported; instead, we noted that studies based on larger samples also tend to report stronger effect sizes. Results of the study indicate that the correlation between 9-HPT and PROMs is strong, although the constructs measured by these instrument does not fully overlap. The correlation between 9-HPT and PROMs was stronger in larger studies and when samples include a sizeable subgroup of PwMS with severe disability, pointing out the importance of sample diversity.