Peaceful was ridden by Seamie Heffernan when she made her track debut in a seven furlongmaiden race at Leopardstown Racecourse on 15 August and started at odds of 10/1. After becoming upset in the starting stalls she was never in serious contention, and came home ninth of the fourteen runners, three and three quarter lengths behind the winner Ridenza. On 10 October the filly was partnered by he trainer's son Donnacha O'Brien when she started the 8/11 favourite for a maiden over one mile at Thurles Racecourse and recorded her first success as took the lead two furlongs from the finish and drew away to win by seven lengths from Indian Lilac. For her final run of the season Peaceful was sent to England to contest the Listed Montrose Stakes on heavy ground at Newmarket Racecourse on 2 November and started the 3/1 favourite in a seven-runner field. With Donnacha O'Brien in the saddle she was among the leaders from the start and kept on well in the closing stages to finish second, beaten a neck by the 20/1 outsider Born With Pride.
2020: three-year-old season
The flat racing season in Ireland was disrupted by the COVID-19 Pandemic and the Irish 1000 Guineas was run three weeks later than usual on 13 Junebehind closed doors at the Curragh. Ridden by Heffernan, Peaceful started the 3/1 second favourite behind Albigna in an eleven-runner field which also included So Wonderful, Fancy Blue and New York Girl. Peaceful settled in second place behind the outsider Valeria Messalina before gaining the advantage a furlong and a half from the finish and stayed on well to win by two lengths and a head from Fancy Blue and So Wonderful. After the race Aidan O'Brien said "Seamus has been delighted with her all the time. He rides her in all her work. Everything has gone very smooth with her. She will get further than a mile so a mile here on beautiful ground really suited her... She's a lovely filly." On 5 July Peaceful was sent to France to contest the Prix de Diane over 2000 metres at Chantilly Racecourse in which she was ridden by Heffernan and went off the 3.9/1 second choice in the betting behind Alpine Star. After racing in mid-division she briefly struggled to obtain a clear run before finishing strongly to take third place, beaten a short neck and a head by Fancy Blue and Alpine Star.
Pedigree
Peaceful is inbred 3 × 4 to Northern Dancer, meaning that this stallion appears in both the third and fourth generations of her pedigree. She is also inbred 4 × 4 to the broodmare Special.