<jats:title>Abstract</jats:title><jats:p>Polymorphic behavior of 1,3‐<jats:italic>rac</jats:italic>‐palmitoyl‐stearoy 1‐2‐oleoylglycerol, 99.9% purity (POS) was examined by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), solubility measurements and optical microscopy in comparison with 1,3‐dipalmitoyl‐2‐oleoylglycerol (POP) and 1,3‐distearoyl‐2‐oleoylglycerol (SOS). Melt crystallization and solvent crystallization were examined for the occurrence of metastable and stable polymorphs. The number of independent polymorphs was four; α,<jats:italic>δ</jats:italic>, pseudo<jats:italic>β′</jats:italic> and<jats:italic>β.</jats:italic> The lowest melting form, α, was identical to that commonly observed in POP and SOS lowest melting forms. As to the highest melting form,<jats:italic>β</jats:italic>, the XRD shortspacing pattern was identical to<jats:italic>β</jats:italic><jats:sub>1</jats:sub> of POP and SOS. This is consistent with crystal habit:<jats:italic>β</jats:italic> single crystals of POS showed the same shape as those of β<jats:sub>1</jats:sub> of POP and SOS. However, the melting point of<jats:italic>β</jats:italic> (POS), 35.9°C, was lower than those of<jats:italic>β</jats:italic><jats:sub>1</jats:sub> of POP, 36.7°C, and of SOS, 43.0°C. Correspondingly, solubility of<jats:italic>β</jats:italic> of POS was lower than that of β<jats:sub>1</jats:sub> of POP below about 13°C, but higher above 13°C. POS did not possess<jats:italic>β</jats:italic><jats:sub><jats:italic>2</jats:italic></jats:sub>, which is the second stable form in POP and SOS. Two forms of<jats:italic>6</jats:italic> and pseudo<jats:italic>β′</jats:italic> occurred, the latter being more stable. The structural properties of<jats:italic>δ</jats:italic> showed that<jats:italic>δ</jats:italic> is not identical to<jats:italic>γ</jats:italic> previously observed in POP and SOS. Transformation behavior from the metastable to stable polymorphs of POS showed some differences from those of POP and SOS.</jats:p>