Background Nonspecific lipid transfer proteins (LTPs) represent potent pollen and food allergens. However, the allergenic properties of peanut LTP have not been studied. Objective To identify LTP in peanut extract using sera from subjects with peanut allergy and Pru p 3–sensitized subjects from Southern Europe, clone and express this protein, and obtain information on the importance as allergen for these selected patients. Methods Peanut LTP (Ara h 9) was cloned and sequenced by using a combination of bioinformatic and molecular biology tools (PCR, immunoblotting, Basic Local Alignment Search Tool BLAST searches). The immunologic properties of Ara h 9, Ara h 1, Ara h 2, and Ara h 3 were studied by using sera from subjects with peanut and peach allergy from Italy by immunoblotting and allergen microarray technology. Results Two Ara h 9 isoforms—Ara h 9.01 and Ara h 9.02—were cloned and expressed. Ara h 9 represented a minor allergen for subjects with peanut allergy. However, including Ara h 9 as single component for serologic detection of sensitization to peanut by component-resolved diagnosis seems crucial, because the frequency of sensitization to the classic major peanut allergens Ara h 1, Ara h 2, and Ara h 3 was low in these patients from Southern Europe. Conclusion Ara h 9 is a new member of the LTP allergen family that seems to play an important role in peanut allergy for patients from the Mediterranean area.