He was considered a promising actor, quickly working his way up the ranks to become a matinee idol. He so impressed the English-born actress Adelaide Neilson, the most popular Juliet of her time, that she begged him to join her company. For reasons of his own, he declined, but years later Miss Nielson publicly singled him out, describing him as "the greatest Romeo I ever played with." Characterizing him as "a little curly-haired Irishman," she added: "When I played with other Romeos, I thought they would climb up the trellis to the balcony; but when I played with Jimmy O'Neill, I wanted to climb down the trellis, into his arms."