Diggers and cranes put together massive sections of the long-awaited s-shaped bridge last week and the last one was secured on Saturday.
Andy Langley, project manager for Costain Ltd, the landmark bridge's developer, told the Express the finished construction was likely to be unveiled next month.
He said: "We're on target at the minute to complete before Christmas.
"The one thing that makes that difficult to achieve is the high standard of work needed to get the timber decking on the bridge absolutely right.
"It's a very strong, Brazilian wood and hard to work with – but so far everything's gone really well and we hope that will continue."
The bridge, the most ambitious scheme being filmed as part of the Channel 4 documentary series The Castleford Project, links Mill Lane with Aire Street and follows the shape of the weir.
Designed by Renato Beneditti, it is being funded by Wakefield Council with Yorkshire Forward and English Partnerships.
Mr Langley said work on the bridge this week included welding the sections together.
He added: "We also then have to add the timber decking, put in the handrails – and install lighting in them – with the benches, as well as carry out work on the two approaching paths.
"The general reaction from the public has been positive and large crowds came down to watch the final piece go into place on Saturday which was great."
The Castleford Project, presented by Grand Designs' Kevin McCloud, has been following 11 projects around the town since 2003, including improvements to the town centre, Tickle Cock underpass and community schemes in Ferry Fryston, Cutsyke, New Fryston and Wilson Street.

l What do you think about the new bridge? Send your views in to the Express by emailing editorial@pandcexpress.co.uk or writing to the Pontefract and Castleford Express, 12 Bank Street, Castleford, WF10 1HZ.