As a three-year-old she won the Classic 1000 Guineas at Newmarket and then returned from a surprising defeat in The Oaks to beat The Derby winner Hermit in the St Leger at Doncaster.

[2] She was foaled in 1864 at Oakley Hall, the stud farm of Colonel (later General) Mark Pearson which was located twenty miles outside of Oakham in Northamptonshire.

[7] Achievement made her first appearance in April at Newmarket's Craven meeting when she started at odds of 4/7 for the four furlong Beacon Stakes and won by two lengths.

She next ran at the Derby meeting at Epsom where she started joint favourite for the Woodcote Stakes with a colt named Hermit and won by three lengths.

She ended the season with eleven wins and two seconds in thirteen races and £10,387 in prize money[8] Her two defeats were ascribed to either a lack of stamina or to respiratory problems, and there were some claims that she was a roarer.

After appearing to have every chance in the straight and briefly taking the lead she weakened in the closing stages before dead-heating for second place with Romping Girl, a length behind Hippia.

[12] Her performance renewed suspicions raised after her previous defeats that she had problems with her "pipes",[11] while other explanations included over-training and an inability to cope with an uphill finish.

[16] Two days after her win in the St Leger, Achievement faced Hermit again in the Doncaster Cup over two miles five furlongs and won by three quarters of a length.

[19] In May 1886 The Sporting Times carried out a poll of one hundred racing experts to create a ranking of the best British racehorses of the 19th century.

Achievement was ranked in the top ten by nine of the contributors, placing her twenty-seventh among all horses and making her the sixth highest-rated filly or mare behind Virago, Plaisanterie, Crucifix, Blink Bonny and Wheel of Fortune.