Police have released an image of a youth they want to speak to in connection with the attack which took place in Brownhills.
A 16-year-old has already been arrested in connection with the Chester Road attack and has since been released on police bail.
Police have now released a CCTV image of a second youth they want to speak to in relation to the attack which happened at around 4pm on February 11.
A Walsall Police spokesman said: "Do you recognise this youth?
"We want to speak to him after a 15-year-old boy was attacked by a group of teens and had a machete pulled on him, and had £200 stolen.
"We arrested a 16-year-old in connection with the attack, which took place on Chester Road, Brownhills at 4pm on 11 February. He has been released on police bail while enquiries continue and we now want to trace this youth.
"The images aren’t great quality but the youth was wearing a black puffer jacket, black trousers, a black cap and a gold chain.
"Anyone with information is urged to contact us via Live Chat at west-midlands.police.uk from 8am-midnight, call 101 or call Crimestoppers anonymously on 0800 555 111, quoting reference 20WS/40514F/21"