Wozniacki, seeded ninth, was handed a heavy defeat by Czech Petra Cetkovska, while 12th seed Ivanovic lost in straight-sets to Eugenie Bouchard.
Wozniacki was unable to break serve at all during her 6-2 6-2 defeat to Cetkovska out on Court Two.
Cetkovska's more aggressive game reaped rewards on the grass as she hit 30 winners to her opponent's six.
Over on Centre Court, Bouchard followed in the footsteps of close friend Laura Robson but defeating a highly-ranked seed.
Less than 24 hours after Robson had knocked out 10th seed Maria Kirilenko, Canadian Bouchard claimed the scalp of former world number one Ivanovic.
Playing on Centre following a last-minute switch which was a result of Victoria Azarenka's withdrawal due to injury, Bouchard was clearly the better player as she posted a 6-3 6-3 win over Ivanovic, seeded 12th this year.
The 19-year-old - who won junior Wimbledon last year - certainly did not seemed fazed by her surroundings. She returned the better and was constantly threatening Ivanovic's serve which she went on to break five times in total.
She will next face Spain's Carla Suarez Navarro, the 19th seed, for a place in the last 16.
Bouchard said: "I was really happy to find out we would change courts.
"I found out 20 minutes before the match, so had a little change of routine but it worked out fine.
"It was my first time so I was really excited. It was kind of a big deal to me and was really cool. To play on Centre Court at Wimbledon is what everyone wants to do.''
Bouchard and Robson's friendship led them to make their own spoof video of the number-one single 'Gangnam Style' which went viral on the internet.
And Bouchard - Genie to her friends - admits she loves catching up with the British number one when their schedules allow.
"I would say she is my closest friend on tour for sure,'' said Bouchard.
"I try not to have too many friends, but a few is good. We are in her home town so it's fun.
"Every time we are at the same tournament we hang out and stuff. It is nice to have someone who is going through the same things as you.''