"We want to draw attention to imbalances in family life, the rising divorce rate, the drop in the age of marriage," Ghannouchi said in a recording broadcast on private radio station Mosaique FM.
Recalling that Prophet Mohammed married wife Khadija when she was more than 40, the Ennahda chief said he wants to "encourage young people to wed women of advanced age."
"Today, 30, 35, and 40, is still young," he said, telling older women not to give up "hope of marrying."
"We also encourage youths and men not to be put off by divorcees. Our divorced girls deserve respect."
Ghannouchi was speaking on women's day, an annual holiday in Tunisia commemorating a 1956 law granting women several new rights and abolishing polygamy and men's right to repudiate women.
"We assure you we are determined to achieve greater equality for men and women," Ghannouchi said.
"Ennahda will not impose any particular clothing on women, the hijab for instance. It is a woman's right to be veiled (or) not to be veiled," the Ennahda leader added.
The Islamist party won Tunisia's first free elections on October 23, 2011 after the uprising that overthrew President Zine El Abidine Ben Ali earlier that year.
It has said several times it will respect women's established rights, though its opponents accuse it of wanting to go back on them.
Tunisia is preparing for a parliamentary election on October 26 and a presidential election on November 23.