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Purpose Iloperidone (Ilo) is an antipsychotic drug having low and pH-dependent solubility, hence less bioavailability. Thus, the aim of this study was to prepare and characterize binary (TAPOL B) and ternary complexes (TAPOL T) of drug with Kolliphor P-188 and tartaric acid to improve solubility. Further, sublingual tablets incorporating ternary complex were formulated to improve the dissolution. Methods Preliminary screening studies were conducted to select the acidifying agent and polymer based on saturation solubility studies. Binary and ternary complexes were prepared by the melting method. Complexes were characterized by DSC, powder Xray diffraction (PXRD), FTIR, microenvironmental studies, and in vitro dissolution studies. The sublingual tablets of ternary complexes were prepared by the direct compression method and evaluated for weight variation, disintegration time, and dissolution studies. Results Based on solubility studies, Kolliphor P-188 and tartaric acid were selected as polymer and acidifying agents. DSC studies and FTIR spectra showed the interaction of drugs with polymer and acidifying agents. PXRD spectra showed the crystalline nature of complexes. Microenvironmental studies carried out in pH 6.8 showed a drastic decrease in pH with ternary complex as compared with binary complex. Dissolution studies showed an increase in dissolution, TAPOL T > TAPOL B > drug. The sublingual tablets showed disintegration time < 30 s and more than 80% of a drug released within 10 min. Due to the presence of tartaric acid and polymer, solubility of the drug increases tremendously.Conclusion The present study demonstrates the increase in solubility and release of Iloperidone due to the microenvironmental pH effect from sublingual tablets. Hence, microenvironmental pH modification is a good approach to increase drug solubility and dissolution. Keywords Iloperidone . Tartaric acid . Kolliphor P-188 . Ternary complex . Microenvironmental pH . Sublingual tablets Highlights • Binary and ternary complexes of Ilo were formulated.• Kolliphor P-188 and tartaric acid were optimized as a polymer and an auxiliary agent. • Tartaric acid accelerated the dissolution efficiency of the drug due to pH change. • DC tablets showed ≥ 80% release within 5 min for 12 mg, maximum strength.