Purpose This in vitro study was conducted to compare the discoloration of a flowable self-adhesive composite, a highly filled composite adhesive, and a liquid polish applied highly filled composite adhesive for bonded lingual retainers. Methods Thirty composite discs were fabricated and divided into three groups: group 1, flowable self-adhesive (GC Ortho Connect™ Flow [GCO], GC Orthodontics, Tokyo, Japan); group 2, highly filled composite adhesive (Transbond™ LR [TLR], 3M Unitek, Monrovia, CA, USA); and group 3, highly filled composite adhesive with liquid polish (TLR and BisCover LV™ [TLRB], BISCO Inc, Schaumburg, IL, USA). L*a*b* values were measured by spectrophotometer prior to (T0) and following (T1) immersion in coffee. T1 − T0 differences were calculated as ∆L*, ∆a*, ∆b*, and ∆E*ab values. The Shapiro–Wilk test was performed to determine whether the data were normally distributed. The values that did not fit the normal distribution were evaluated with the Kruskal–Wallis one-way analysis of variance (ANOVA), and Dunn’s test was used for multiple comparisons. The level of significance was p < 0.05. Results The difference between the TLR and TLRB groups was statistically significant for ∆E*ab (P = 0.007). ∆E*ab value of TLR group was greater than ∆E*ab value of TLRB group. The differences between the GCO and TLR groups (p = 0.001) and the TLR and TLRB groups (p = 0.010) were statistically significant for ∆a*. ∆a* values of GCO and TLRB groups were greater than ∆a* value of TLR group. The difference between the TLR and TLRB groups was statistically significant (p = 0.003) for ∆b*. ∆b* value of TLR group was greater than ∆b* value of TLRB group. Conclusions Using a Transbond LR polished with BisCover LV or only GC Ortho Connect Flow for lingual retainer bonding reduces coffee-induced discoloration.