Hydroxyapatite is a mineral composed of hydrated calcium phosphates. As it is the main mineral component of human bone, it is widely used in the fabrication of alloplasts for bone tissue regeneration treatments, known as scaffolds [1][2]. Scaffolds serve as a cellular matrix for the development of new bone tissue; therefore, they must have a porous structure, adequate mechanical strength, and be composed of biocompatible material [3]. To meet these criteria, additive manufacturing techniques, such as fused deposition modeling (FDM) 3D printing, are employed as an alternative for controlling structure and mechanical strength. However, if the printer operates by extruding thermoplastic material, it is necessary to synthesize polylactic acid (PLA) filament loaded with hydroxyapatite to incorporate the bioceramic into the scaffold [4]. Hydroxyapatite can be obtained through various synthesis routes or from synthetic or natural resources. In this study, hydroxyapatite was extracted from the byproduct of the Arapaima gigas fish and used to produce filaments for 3D printing. The scales were subjected to chemical treatment with NaOH and thermal treatment with sintering at 600 ºC in an oxygen-rich environment. The characterizations performed were TG, DTG, DSC, FTIR, and SEM. After these characterizations, the sample was subjected to a thermal treatment at 700 ºC, followed by the same analyses. The filaments were produced by extrusion and were loaded with 1% w/w of hydroxyapatite extracted from the scales of Arapaima gigas. The filaments were subjected to tensile testing according to ASTM C1557-20. Thermal analysis revealed that the sample sintered at 600 ºC did not undergo complete removal of organic volatiles, with mass losses of 3.6% in the range of 75 ºC – 100 ºC due to residual water; 1.1% in the range of 280 ºC – 700 ºC due to collagen residue; and 2.93% between 600 ºC – 742 ºC due to the loss of structural water from hydroxyapatite. The sample sintered at 700 ºC showed little mass loss, with a total loss of 1.68%, and a maximum degradation temperature at 619 ºC, related to the structural water present in hydroxyapatite. In both samples, FTIR analyses revealed the characteristic bands of PO₄³⁻ anions at 1091 cm⁻¹; 1022–1018 cm⁻¹; 602–563 cm⁻¹, and the presence of CO₃²⁻ ions at 1450 cm⁻¹, 1411 cm⁻¹, and 871 cm⁻¹. Scanning electron microscopy (SEM) micrographs showed that the samples sintered at 600 ºC presented agglomerates of inorganic particulates without a defined morphology. Sintering at 700 ºC promoted the growth of particulates with polygonal shapes, tending toward hexagonal formation.