Gyimah, who represents the constituency of East Surrey, announced the news on social network site Twitter this morning.
Confirmation of his brief comes almost a week after he was appointed as under secretary of state at the Department for Education (DfE).
Berkshire-born Gyimah takes over from former childcare minister Elizabeth Truss, who was promoted to Environment Secretary as part of a Cabinet reshuffle last Tuesday.
Gyimah was elected to parliament in May 2010 and was appointed as parliamentary private secretary to Prime Minister David Cameron in September 2012 before becoming a government whip in October 2013.
The 37-year-old studied philosophy, politics and economics at Oxford University and began a career in the business sector after gaining a place on a graduate scheme at investment bank Goldman Sachs.
A spokesman for the DfE confirmed that Gyimah will be responsible for the childcare brief and said the length of time between last week’s reshuffle and today’s announcement was “completely normal” despite concerns from the sector.
On Friday, the Pre-school Learning Alliance and the Professional Association for Childcare and Early Years (Pacey), expressed their concerns at the delay and warned that it could suggest that childcare does not figure highly in the government’s future plans.
However, Neil Leitch, chief executive of the Pre-school Learning Alliance, has welcomed Gyimah's appointment and hopes he will work collaboratively with the sector.
He said: "His appointment is an opportunity for a fresh start – a chance for policymakers to work much more collaboratively with the sector in order to support the development of a high-quality, sustainable childcare system.
“This move has come at a particularly crucial time for early years with several changes due to come into effect later this year, such as the revised Early Years Foundation Stage framework, the extension of the two-year-old offer, the introduction of childminder agencies and the implementation of the special education needs code of practice.
"As such, we look forward to working with Mr Gyimah and his team at the DfE to ensure that the sector is adequately supported during this time of transition, as well as in the longer term.”
Victoria Flint, head of communications at Pacey, added: "We look forward to working with Mr Gyimah and his team to address some of the most pressing challenges for families and childcare professionals during a critical time for the sector.
"Above all, we are interested in exploring with Mr Gyimah our ideas for supporting greater recognition of the fantastic skills, efforts and expertise of childcare professionals, who work every day to give the youngest in society the very best start in life."
In addition to Truss’s departure, the reshuffle also saw former Treasury minister and Conservative MP for Loughborough Nicky Morgan replace Michael Gove as Education Secretary.