The Gleann southpaw stopped Jamaican Jerone Ennis in the final round of their semi final in the Bahamas.
The youngster claimed a comfortable quarter final win last night against Samoan Ah Tong Marion and upgraded his bronze to silver here.
For the most part it was an intensely cagey bout and barely a punch was thrown in the opener as both boxers feinted, trying to suss each other out.
The probing southpaw backhand of Johnston began to find a home as the fight opened up slightly in the second.
Johnston then grabbed the bout by the scruff of the neck in the final round, downing Ennis with a huge straight left. The Caribbean fighter rose, but was put back down straight away and Johnston claimed a knockout silver medal win.
The Antrim boxer joins middleweight Kane Tucker in tomorrow’s deciders after the Newry fighter defeated Canadian Satwinder Thind.
In the final, Johnston will box England’s Mark Dickinson.
Colm Murphy and John Moran were forced to settle for bronze earlier this evening after semi final defeats.
Commonwealth Youth Games VI, Bahamas
Wednesday July 19th
(L16) 60kg – Dominic Bradley lost to Rhys Edwards (Wales) 2-3
(L16) 56kg – Colm Murphy beat Ahmed Faraz (Scotland) 5-0
Thursday July 20th
(QF) 49kg – John Moran beat Seanoa Hall (Samoa) 5-0
(QF) 56kg – Colm Murphy beat Sean Finnigan (Canada) 5-0
(QF) 75kg – Kane Tucker beat Reekie Ryan (Scotland) 4-1
Friday July 21th
(QF) 52kg – Kian Bittles lost to Allicock Keevin (Guyana) split
(QF) 69kg – Anthony Johnston beat Ah Tong Marion (Samoa) 5-0
Saturday July 22nd
(SF) 49kg – John Moran lost to James Probert (Wales) 0-5
(SF) 56kg – Colm Murphy lost to Joshua Fitzpatrick (Australia) 2-3
(SF) 75kg – Kane Tucker v Satwinder Thind (Canada) 5-0
(SF) 69kg – Anthony Johnston v Jerone Ennis (Jamaica) TKO3
Sunday July 23rd
(F) 69kg – Anthony Johnston v Mark Dickinson (England)
(F) 75kg – Kane Tucker v Aaron Bowen (England)
Northern Ireland Team
49kg – John Moran (Illies GG) (Bronze)
52kg – Kian Bittles (Holy Trinity)
56kg – Colm Murphy (St George’s) (Bronze)
60kg – Dominic Bradley (captain) (Errigal)
69kg – Anthony Johnston (Gleann) (Silver, at least)
75kg – Kane Tucker (Holy Trinity) (Silver, at least)