Mixed Plasmodium malaria infections can lead to severe malaria. This systematic review and meta-analysis aimed to explore the prevalence of severe mixed Plasmodium malaria infection and to compare it with the prevalence of severe P. falciparum malaria mono-infection across the included studies. Original English-language research articles from PubMed, Scopus, and ISI Web of Science were identified and screened. Articles reporting the number of mixed infections and the number of severe mixed infections were used to determine the main outcome of this study, while the number of P. falciparum infections and the number of severe P. falciparum infections were used to determine the secondary outcome of this study. For the main outcome, the pooled prevalence and 95% confidence interval (CI) of severe mixed infections was analysed using STATA software version 15.0 (Stata Corp, College Station, TX, USA). For the secondary outcome, the rate of severe mixed infections compared to severe P. falciparum infections was analysed using the meta-analysis approach, and summary odds ratios (ORs) and 95% CIs were calculated. Random-effects models were used to produce the summary ORs. The Mantel-Haenszel method and calculated I2 were also reported to test whether there was heterogeneity among the included studies. Publication bias was also assessed using funnel plots. The meta-analysis of secondary outcomes was conducted using Review Manager 5.3 software (Cochrane Community). A total of 894,561 malaria patients were reported in all 16 included studies. Overall, a pooled analysis showed that 9% (2,006/35,768, 95% CI 7.0-12.0%) of patients with mixed Plasmodium infection had severe mixed infection. A meta-analysis of 14 studies demonstrated that patients with mixed Plasmodium infection (1,999/35,755) and patients with P. falciparum malaria (9,249/294,397) had an equal risk of developing severe malaria (OR 0.93, 95% CI 0.59-1.44). Both mixed infection and P. falciparum mono-infection showed a similar trend of complications in which severe anaemia, pulmonary failure, and renal impairment were the three most common complications found. However, patients with mixed infection had a higher proportion of severe anaemia and pulmonary complications than those with P. falciparum infection. Moreover, patients with mixed infection had a higher proportion of multiple organ failure than those with P. falciparum mono-infection. Mixed Plasmodium spp. infections were common but often unrecognized or underestimated, leading to severe complications among these malaria patients. Therefore, in routine clinical laboratories, using an accurate combination of diagnostic procedures to identify suspected patients with mixed infections is crucial for therapeutic decisions, prompt treatment, and effective patient management.