The agency won the business following a pitch against CheethambellJWT and M&C Saatchi.
Mother’s capture of the business follows the decision to call a pitch last month. The incumbent agency DLKW Lowe, which created last year’s "best trips last a lifetime" campaign, decided not to repitch.
Paul McClenaghan, the Halfords group commercial director, said. "We have started on a journey to reposition Halfords as a provider of expert help and services. Working with Mother is yet another important step towards this transformation.
"Our aim in the agency pitch process was to find a partner who can bring our new proposition alive for customers. We are impressed by Mother's inspirational ideas for this next important step in the evolution of Halfords brand."
Sara Tate, the head of brand and new business at Mother, said. "The Mother Team has been greatly impressed by the ambition and desire of Halfords to transform their brand and business. They are enthusiastic and great to work with. We are looking forward to going on a great journey with them."