We investigated the quantity and concentration of toxins in different parts and in different growth phases of Lepiota brunneoincarnata mushroom. The amatoxins and phallotoxin levels were measured using the reversed phase high-performance liquid chromatography (RP-HPLC) method. Alpha amanitin (2.38 ± 0.70 mg/g) was followed by beta amanitin (1.97 ± 0.52 mg/g) and gamma amanitin (0.04 ± 0.01 mg/g) in trace amounts; it did not contain any phallotoxin. The cap part is richer in amatoxins than the stipe part. While medium mushrooms were quite rich in amatoxins, less levels of toxin were measured in fully developed mushrooms. The study showed in detail the toxin concentrations of L. brunneoincarnata with regard to different developmental stages and different segments.