[2] Wanhalla was appointed a lecturer in history at the University of Otago in 2005, and rose to become a full professor there in February 2022.

She investigated the relationships of US servicemen with Māori and Pasifika women in New Zealand as part of the Marsden project Mother's Darlings, led by Judith Bennett.

[6][7] She is co-leader of the Marsden-funded project Te Hau Kāinga: Histories and Legacies of the Māori Home Front, 1939–45.

[11] In 2014, Wanhalla was awarded a Royal Society Te Apārangi Rutherford Fellowship, worth $800,000, for a project titled Marriage: The Politics of Private Life in New Zealand.

Her nomination stated she "has successfully broadened understanding of how intimate relations, inclusive of affectionate bonds, sexual violence, and the emotional legacies of global war in indigenous societies, are deeply entwined with colonial policy and practice.