Alan Leah, 33, admitted cornering the child in his car on two separate occasions in October 2020.
He put his hand down the girl's pants and then called her a "pussy" and "weak" when she pushed him away.
During the second incident a few days later, Leah exposed himself while driving and told the young girl to "suck it", but she refused.
County Court Judge Anne Hassan on Friday described the offending as serious as she sentenced Leah to two years and six months behind bars.
He will be eligible for parole after 18 months and has already served seven months of that sentence.
Leah's pregnant partner rushed over and kissed him as security guards tried to lead him from the court.
Judge Hassan noted Leah had initially pleaded guilty to the offending in October 2022 after the victim was cross-examined in court.
He tried to change his plea to not guilty earlier this year but the judge refused his application.
In sentencing, Judge Hassan found Leah had no remorse for his actions and he continued to deny the offending.
The young girl had experienced suicidal ideation and anxiety as a result of Leah's actions, the judge said.
"She was a child and you were an adult," Judge Hassan told Leah.
"It's clear you developed a sexual interest and you took advantage of her - (the girl) was effectively trapped."
Leah's prospects of rehabilitation were reasonable as he was abstaining from drugs, had a job lined up and a stable partner with a baby on the way, Judge Hassan said.
He had been deemed suitable to complete a community work order but the judge said a more stern sentence was required.
"I must denounce your conduct," Judge Hassan said.
Leah will be placed on the sex offender's register for the next 15 years.
Lifeline 13 11 14
Kids Helpline 1800 55 1800 (for people aged 5 to 25)
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
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