[2] In 2001, Colin Groves included the Callitrichids in the family Cebidae, which also includes capuchin monkeys and squirrel monkeys, but in 2009 Anthony Rylands and Russell Mittermeier reverted to older classifications which considered Callitrichidae a separate family.

[10] The fur on its back is variegated black and yellow, with pale legs, feet and chest.

[14] Vocalizations that have been recorded include whistles, twitters, trills, loud or soft sharp notes, sneezes and long rasps.

[10] Body postures and displays that reveal more of the white coloration, such as standing on hind legs and piloerection, tend to be associated with aggression.

To the extent Geoffroy's tamarin uses large vertical supports for travel, it uses them most often for ascending rather than descending.

The flycatchers and tamarins have different patterns of activity, which minimizes competition for similar food sources.

[14] Geoffroy's tamarin has a varied diet that includes fruits, insects, exudates (gums and saps), and green plant parts.

[10] A study by Paul Garber estimated that the diet was made up of 40% insects, 38% fruit, 14% exudates (almost entirely from Anacardium excelsum cashew trees), and 8% other items.

[10][16] Another study, on Barro Colorado Island, showed 60% fruit, 30% insects and 10% green plant parts, including large amounts of elephant ear tree (Enterolobium cyclocarpum) sap.

[3][16] It generally hunts for insects by making quick movements on thin, flexible supports.

[16] In one study, Geoffroy's tamarin drank water from the corollas of Ochroma limonesis flowers.

[14] Both polyandrous and polygynous mating occurs, and males contribute heavily to parental care.

[18] In Colombia, it occurs on the Pacific coast west of the Andes, south to the Rio San Juan.

[6] The eastern boundary of its range in Colombia was once thought to be the Rio Atrato, but has been reported further east, including the Las Orquídeas National Natural Park.

[6] Older sources sometimes report the species occurring in southern Costa Rica, but these are most likely erroneous.

[3] The main threat is deforestation, which is causing population declines in some areas despite its ability to adapt to some modifications of its habitat.

[3] A 1985 study in Panama concluded that Geoffroy tamarin population densities are higher in areas where human access is limited.

While hunting decreases the population, cutting mature forest for agriculture provides more areas of secondary growth, which is beneficial for the tamarin.