Hippeastrum stapfianum (Kraenzl.) R.S.Oliveira & Dutilh (Amaryllidaceae) is an endemic plant species from the Brazilian savannah with biological and pharmacological potential. This study evaluated the effects of ethanol extract from H. stapfianum leaves on acetylcholinesterase enzyme activity and the action on nuclear receptors PPAR-α and PPAR-γ. A gene reporter assay was performed to assess the PPAR agonist or antagonist activity with a non-toxic dose of H. stapfianum ethanol extract. The antioxidant capacity was investigated using DPPH• scavenging and fosfomolybdenium reduction assays. The identification of H. stapfianum‘s chemical composition was performed by gas chromatography–mass spectrometry (GC-MS) and HPLC. The ethanol extract of H. stapfianum activated PPAR-α and PPAR-γ selectively, inhibited the acetylcholinesterase enzyme, and presented antioxidant activity in an in vitro assay. The major compounds identified were lycorine, 7-demethoxy-9-O-methylhostasine, and rutin. Therefore, H. stapfianum is a potential source of drugs for Alzheimer’s disease due to its ability to activate PPAR receptors, acetylcholinesterase inhibition activity, and antioxidant attributes.