The Transport Minister polled 1,429 votes to beat former vice-president Datuk Chua Jui Meng who got 917.
Ong said he now had more than one task to tackle.
On working with newly-elected deputy president Datuk Seri Dr Chua Soi Lek, he said he could work with anybody.
Newly-elected MCA Deputy President Datuk Seri Dr Chua Soi Lek says he is ready to help re-invent the party.
Chua said he would continue to work towards his vision for the party and community despite his defeat.
His vision, as outlined in his manifesto, included fighting for fairness for all Malaysians and eradicating corruption