Spring

Before the start of the 1876 flat season, Petrarch was bought for 10,000 guineas (£10,500) by Lord Dupplin.^[13] Early in the year, Petrarch was favourite in the betting lists for both the 2000 Guineas and the Derby.^[14] In April however, he took part in a public trial race in which he was beaten by Lord Dupplin's other classic entry Kaleidoscope. Although Dawson had warned the owner that Petrarch was not fully fit, the trial convinced Dupplin that Kaleidoscope was the better horse and he wagered accordingly.^[15] As a result, Kaleidoscope was made favourite for the 2000 Guineas, with Petrarch starting a 20/1 outsider in a field of fourteen runners. Ridden by the little-known lightweight jockey Harry Luke,^[16] Petrarch moved alongside the early leader Camembert three furlongs from the finish and then accelerated clear of the field. He won "in a canter"^[17] by three lengths from Julius Caesar, with Kaleidoscope third. Contemporary reports described his victory as one of the easiest ever seen in the race. The crowd's response to the upset was muted, and the bookmakers were almost equally subdued, as some had taken bets at odds of up to 40/1 on the winner.^[6] At least one commentator stated that Petrarch's poor performance in the earlier trial had been a deliberate ploy by Dupplin and his confederates to obtain better odds against the colt.^[18]

Summer

At Epsom on 31 May, Petrarch started 2/1 favourite for the Derby, with the Mineral colt, now named Kisber being the second choice in the betting. Petrarch took the lead in the straight, but when Kisber emerged to challenge him a furlong from the finish he quickly faded from contention and finished fourth of the fifteen runners.^[19] It was later suggested that Petrarch's connections had never intended to win the race,^[20] and that his poor performance had been deliberately engineered as part of a betting strategy.

In June Petrarch was sent to Royal Ascot where he won the thirteen furlong Prince of Wales's Stakes from Julius Caesar. He failed to reproduce his form in two other races at the meeting, finishing fourth to Coltness in the Biennial Stakes and last of the three runners behind Morning Star in the second leg of the Triennial Stakes.^[21] One of the leading gamblers of the day, Lord Dudley, created a controversy when he refused to pay the £9,000 he had lost by wagering on Petrarch in his Ascot defeats, claiming that the horse had not been allowed to run on its merits.^[3]

Autumn

At Doncaster in September, the Derby winner Kisber started 7/4 favourite for the St Leger, with Petrarch, ridden my Jem Goater on 9/1. Petrarch was not among the early leaders as Kisber set a strong pace. Approaching the turn into the straight, Petrarch moved up to join the favourite, with the 100/1 outsider Wild Tommy also making good progress. With Kisber quickly dropping back in the straight, the race became a struggle between Petrarch and Wild Tommy and Goater made vigorous use of his whip and spurs as Petrarch stayed on gamely to win by a neck after a "fine race".^[22] As at Epsom and Ascot, there were rumours that the race had not been entirely fair: it was reported that Petrarch had been heavily backed to win by Kisber's owners, the Baltazzi brothers, who therefore stood to profit from the poor running of their own horse.^[23] According to press reports, bookmakers paid out £80,000 on winning bets on the race.^[24]

Petrarch earned prize money of £11,700 in 1876, making him the most financially successful horse of the year in Britain.^[25]