The special events, which will be held at Sentry Hill, are due to take place on June 6 and 26.
There will be 250 guests at each garden party and guests from all sections of Newtownabbey society will be invited.
Invitations will be sent to the voluntary, community, service and business sectors.
In a statement a council spokeswoman said: "When the 50th Anniversary Garden Parties were being planned the Council was keen to ensure that the dates did not clash with any of the Secretary of State's garden parties in Hillsborough Castle. Information on the dates of the Hillsborough garden parties was not available at that stage and knowing that they are usually held in late May or early June, it was decided to plan the Sentry Hill garden parties for later in June.
"The Council agreed that the Annual Meeting should be re-arranged for Monday 9 June."
A council source, who did not want to be named, questioned the need for two garden parties rather than one.
"I find it strange that the council is staging two parties at Sentry Hill, one should be enough. Given recent stories about the council's £28m debt, is this not a bit of a waste of money?"
The council has also released figures on 50th Anniversary branding costs.
Approximately £6,357 has been spent on changing logos for stationery, vehicle signs and flags.
£900 has been spent on branding a small number of vehicles in the council fleet.
A sign at Mossley Mill and the Valley Leisure Centre have also been re-branded using a vinyl graphic technique at a cost of around £100.
Furthermore, the council has bought 12 outdoor banners costing £1,260, six upright stands to use at indoor events at £840, and 18 flags have been ordered at a cost of £3,257.
Meanwhile a £16,000 sculpture has also been unveiled at the Valley Leisure Centre.
'Endeavour' was designed by Stephen Todd and officially unveiled by Mayor Nigel Hamilton to mark the council's 50th anniversary.
Designed to capture the sense of sporting movement and personal endeavour, the sculpture is fabricated in brushed stainless steel.
Mr Todd said he wanted to create a form that was both eye catching and inspiring to all those who will use the newly refurbished Valley Leisure Centre.
Illuminated at night by bright up lighters, the sculpture intends to be a bold landmark for the local community. Based on the combined form of a footballer ready to kick a ball, a netballer ready to throw a ball or even a sprinter getting ready to run, Endeavour hopes to capture the essence of many sporting activities.
The sculpture was funded by the Council as part of the refurbishment of the Valley Leisure Centre.