Jackson had been due to perform at the state fair on Wednesday while the country group were set for Friday.
Organisers said a Maroon 5 and Train show planned for Thursday will now move to the nearby Conseco Fieldhouse, with proceeds going to a remembrance fund.
The stage collapsed on Saturday after strong winds blew its rigging over.
About 45 other people were injured while 12,000 concert-goers awaited the start of a concert by country group Sugarland.
Investigators have put incident down to unforeseeable and isolated high winds, but have launched a further inquiry.
On their website, Lady Antebellum said it had been a "difficult decision" to cancel their show.
The group tweeted: "We're so sorry to cancel this Friday's show, our thoughts are with Indy."
Jackson also wrote on Twitter : "Heartbroken. Prayers and love to Indiana."
Organisers said tickets previously purchased for the Maroon 5 and Train show will be honoured at the new venue where a number of stage, security and restaurant staff are volunteering to make the concert possible.
All proceeds will benefit the Indiana State Fair Remembrance Fund.
The fair reopened on Monday with a memorial service to honour the victims of the collapse.
US concerts by Janet Jackson and Lady Antebellum have been cancelled following a stage collapse that killed five people in Indiana at the weekend.