Periodontitis is a chronic inflammatory disorder often seen in patients with diabetes mellitus (DM). Individuals with diabetes are at a greater risk of developing cardiovascular complications and this may be related, in part, to lipid abnormalities observed in these individuals. The objective of this systematic review is to compile the current scientific evidence of the effects of periodontal treatment on lipid profiles in patients with type 2 diabetes mellitus. Through a systematic search using MEDLINE, EMBASE, PubMed, and Web of Science, 313 articles were identified. Of these, seven clinical trials which met all inclusion criteria were chosen for analysis. Between baseline and 3-month follow-up, there was a statistically significant reduction in the levels of total cholesterol (mean differences (MD) −0.47 mmol/L (95% confidence interval (CI), −0.75, −0.18, p = 0.001)), triglycerides (MD −0.20 mmol/L (95% CI −0.24, −0.16, p < 0.00001)) favouring the intervention arm, and a statistically significant reduction in levels of high density lipoprotein (HDL) (MD 0.06 mmol/L (95% CI 0.03, 0.08, p < 0.00001)) favouring the control arm. No significant differences were observed between baseline and 6-month follow-up levels for any lipid analysed. The heterogeneity between studies was high. This review foreshadows a potential benefit of periodontal therapy for lipid profiles in patients suffering from type 2 DM, however, well designed clinical trials using lipid profiles as primary outcome measures are warranted.