The London-based firm trounced a six-strong shortlist which included entries from Egypt's Youssef Ghali, B & C Associati from Italy, Arca from Manchester, London's Chris Curtis & Elliott Wood, and Hakes Associates.
Designed in collaboration with structural engineer Eckersley O'Callaghan, the bridge will form part of the wider regeneration of the area, which is being driven by Sefton Borough Council.
Bridge-design veteran, RIBA adviser, and judge Renato Benedetti said: 'When judging, it's a pleasure to see a clear and worthy winner emerge.
'Although the presentations and interviews of each shortlisted team were impressive, the Softroom proposal stood out.'
He added: 'Its strong elegant form, clever access ramps and stairs, sustainable economic timber structure and overall aesthetic ethos were the most appropriate and uplifting solution for the site and brief. It was the unanimous choice and I look forward to seeing it built.'
Softroom will now work alongside the council to develop the winning scheme and it is expected work will start on site later this year.