Five cDNA fragments (I–V) representing five P450 isoforms were cloned and a novel P450 cDNA was isolated from Ummeliata insecticeps (Bösenberg & Strand), using the reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends. The full cDNA is 2708 bp in length and contains an open reading frame (ORF) encoding 521 amino acid residues. The putative protein contains the conserved structural and functional regions characteristic of all P450 enzymes. The P450 shows the highest percentage of amino acid identities (47%) with CYP4V18 from Litopenaeus vannamei (Boone, 1931). Phylogenetic analysis showed that the P450 was grouped in the lineage containing some of the CYP4 family members. The GenBank accession number is FN773088. This is the first report of P450 genes cloned in spiders (Araneae).