The preface by James Maidment to Letters from Thomas Percy, D.D., afterwards Bishop of Dromore, John Callander of Craigforth, Esq., and others, to George Paton, which appeared at Edinburgh in 1830, indicates that in his latter years Callendar was reclusive, and a religious melancholic. He died, at an old age, at Craigforth on 14 September 1789.
Callandar presented five volumes of manuscripts, Spicilegia Antiquitatis Græcæ, sive ex veteribus Poetis deperdita Fragmenta, to the Society of Scottish Antiquaries in 1781, shortly after he was elected a fellow. He also presented at the same time nine volumes of manuscript annotations on John Milton's Paradise Lost, of which he had published those on Book I. in 1750. In March 1818 an article on the edition of Book I. of appeared in Blackwood's Magazine, in which it was shown that much in his notes had been borrowed without acknowledgment from the annotations of Patrick Hume in the sixth edition of Paradise Lost (published by Jacob Tonson) in 1695. A committee of the Society of Antiquaries of Scotland reported on the manuscript notes, saying that a comparatively small proportion of were from Hume.
In 1766–8 Callandar brought out in three volumes Terra Australis Cognita, or Voyages to the Southern Hemisphere during the Sixteenth, Seventeenth, and Eighteenth Centuries, partly translated from Charles de Brosses. While this was an influential work for British readers, and timely given the expeditions of James Cook, the content involved adaptation without acknowledgement of the work and maps of de Brosses, and is considered as plagiarism.
In 1779 Callander published An Essay towards a Literal English Version of the New Testament in the Epistle of Paul directed to the Ephesians, in which he gave a metaphrase in English of the Greek idiom. His edition of Two ancient Scottish Poems, the Gaberlunzie Man, and Christ's Kirk on the Green, with Notes and Observations, published at Edinburgh in 1782, contained questionable etymological remarks.
Callander projected other works, including Bibliotheca Septentrionalis, of which he printed a specimen in 1778, and a History of the Ancient Music of Scotland from the age of the venerable Ossian to the beginning of the Sixteenth Century, for which he printed Proposals in 1781.
- Stephen, Leslie, ed. (1886). "Callander, John". Dictionary of National Biography 8. London: Smith, Elder & Co.
- Callander, John. "Early Explorers to the Pacific". Charting the Land on the Ocean Pacific Exploration, 1520-1876. University of Otago Library. Retrieved 27 May 2015.
- Tom Ryan, "Le Président des Terres Australes": Charles de Brosses and the French Enlightenment Beginnings of Oceanic Anthropology, The Journal of Pacific History Vol. 37, No. 2 (Sep., 2002), pp. 157-186, at p. 180. Published by: Taylor & Francis, Ltd. Stable URL: http://www.jstor.org/stable/25169591