Farbrace, who guided the Lions to World Twenty20 glory in Bangladesh, leaves them after honouring only four months of the two-year contract that he signed when they snared him from Yorkshire last December.
However, the former Kent and Middlesex wicketkeeper, who is regarded as one of the most astute coaches in world cricket, has been tempted away from his new position to serve his home country.
The ECB are yet to confirm Farbrace as Moores's number two, but an announcement is expected in the coming days. They have previously admitted holding talks with the 46-year-old.
Sri Lanka are England's first opponents during the Moores and Farbrace era, visiting the United Kingdom in May for a Twenty20 match, five one-day internationals and a two-match Test series.