Toni fired the ball home from close range after 65 minutes, giving Verona victory at Stadio Marc' Antonio Bentegodi, which they share with Chievo.
The goal took the Italian's tally to 16 in Serie A this term - a new record for a Verona player in a single season - and he sits third in the league's scoring charts, two behind Juventus' Carlos Tevez and one shy of Torino forward Ciro Immobile.
Chievo impressed in the first 20 minutes and forced Rafael into a number of saves, but Verona came to life thereafter.
Juan Iturbe, the diminutive 20-year-old Argentinian on loan from Porto and reportedly interesting Liverpool, tormented Chievo with a couple of dazzling dribbles and forced Michael Agazzi into two smart saves. However, it was Toni, 36, who settled the match.
Victory moved Verona to within one point of Parma, who hold the last Europa League qualifying spot, while Chievo remain two points above the relegation zone.
Mauro Icardi also boosted his chance of going to Brazil 2014 with a brace for Inter Milan, but Diego Milito's late penalty miss meant their under-fire coach Walter Mazzarri had to settle for a 2-2 draw at home to Bologna.
Icardi, who is hoping to make Argentina's World Cup squad, twice put the three-time European champions ahead – a predatory early goal preceding a superb curler from the edge of the box – but Michele Pazienza and Panagiotis Kone both pounced on rebounds to score equalisers at San Siro.
Inter had a glorious late chance to win it when Rodrigo Palacio won a penalty, but substitute Milito failed to beat Gianluca Curci, leaving Mazzarri's men without a victory in four outings.
Inter remain fifth, two points behind fourth-placed Fiorentina and only three above Parma, who have a game in hand.
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