Jackson, 22, delivered an emotional speech to thousands of cricket fans at the Melbourne Cricket Ground – something which he then shared on Instagram.
WATCH: Shane Warne's son Jackson delivers an emotional speech at the State Memorial Service
Upon seeing the footage, Elizabeth penned: "I love you Jackson. The Lion would be proud of you. See you soon [heart emojis]."
The 56-year-old model, who was absent from the State Memorial Service, went on to write a message to Shane's daughter Brooke. "Your speech was magical. I love you and see you soon. SW23 FOREVER," she said.
Shane was once the captain of the Australia national team and was widely considered one of the greatest bowlers in cricket history. He was previously in a relationship with The Royals actress Elizabeth - their romance came to an end in November 2013. The duo dated for three years and were at one point engaged, before separating.
The sportsman leaves behind three children Brooke, 24, Summer, 19, and Jackson - all of whom he shares with ex-wife Simone Callahan.
Shane Warne died aged 52 last month
He passed away on 4 March from natural causes and Elizabeth previously paid tribute to her "lionheart". Taking to Instagram, she shared several photos from their engagement and explained that she was going to miss his funeral.
"My heart aches that I can't be in Australia tomorrow for Shane's funeral," she lamented. "I was filming last night and, with the time jump, physically can't get there.
"These pictures were taken in Sri Lanka to celebrate our engagement- we had all our children with us and it was the happiest time. It still hasn't really sunk in that he's gone." She added: "It seems too cruel that all the people who loved him will never have another Lion hug, but our memories will live forever. RIP Lionheart, with love your Luna."
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