Two biographies of Baldassare d'Este have been published by the National Gallery of Art in the systematic catalogues of its collection. Both are given here.
By Joseph Manca, in Italian Paintings of the Fifteenth Century, published 2003:
Baldassare d'Este, who was probably an illegitimate son of the Ferrarese ruler Niccolò III d'Este, was born in Reggio Emilia in 1432. It is not known where he received his artistic education, but he is first documented in 1461 at the court in Milan, where he was at work on portraits of Galeazzo Maria Sforza and his wife. In 1469 Galeazzo allowed Baldassare to work for Borso d'Este in Ferrara, where for the next five years he shared the limelight at the Estense court with Cosmè Tura.
Baldassare specialized in portraiture, recording the features of the Este rulers and their dependents in paintings and medals. His skill led to the unusual commission in 1472 to retouch thirty-six portraits of Borso and to repaint other heads and busts of courtiers in the Hall of the Months frescoes in the Palazzo Schifanoia (finished by spring of 1470). Baldassare also painted religious works, including fresco scenes from the life of Saint Ambrose in the church of San Domenico (1472). Baldassare's middle years are poorly documented, and there is doubt about the extent of his artistic activity in the later 1470s and 1480s, when he is recorded as a military captain in Reggio Emilia; however it seems that by the late 1490s he was again working in Ferrara, where he produced several paintings before his death, which occurred by 1510.
There are only a few surviving secure works by Baldassare, most of them portraits. The Portrait of Tito Strozzi (Vittorio Cini collection, Venice) is signed and dated, somewhat illegibly, to 1493 (or possibly 1499). Some sections of a mural decoration from c. 1500 contain a partly legible inscription that can be read as his signature; these fragments--representing donor portraits, architectural details, and what remains of a Stigmatization of Saint Francis--were originally in the Oratoria della Consolazione in Ferrara, and are now in the Pinacoteca Nazionale there. There are three signed medals of 1472 with portraits of Duke Ercole I d'Este. Of the many portraits and religious paintings attributed to him, the most plausible are a Portrait of Borso d'Este (Castello Sforzesco, Milan), miniature portraits of Borso and Ercole I d'Este (Genealogia Estense, Biblioteca Estense, Modena), and the Portrait of Francesco II Gonzaga in Washington. Baldassare's style, to judge from the certain works and from comments by contemporaries, was skillfully naturalistic; his works were elegant and delicate heirs to the International Gothic style, as opposed to the heroic portrait style that flourished in some parts of Italy in the later quattrocento. His medals, in particular, are refined and lyrical, recalling Pisanello. The flattering naturalism of Baldassare's portraits brought him favor in aristocratic circles in late quattrocento North Italy.
Longhi, followed by some later writers, identified the paintings of an anonymous Ferrarese painter christened by Longhi "Vicino da Ferrara" as the works of Baldassare d'Este, yet this suggestion is unconvincing, as the surviving works by Baldassare are more fluid and refined than the works of "Vicino," whose identity remains undetermined.
 Longhi, Officina ferrarese (1934) 1956, 48-51; (1940) 1956, 137-138; and (1940-1955) 1956, 182-184. Daniele Benati, "Per il problema di 'Vicino da Ferrara' (alias Baldassarre d'Este?)," Paragone 33, no. 393 (1982): 3-26.
By John Graham Pollard, in Renaissance Medals, published 2007:
Baldassare is believed to have been a bastard son of the Marquess Niccolò III d'Este and was born at Reggio. He was working in Milan in 1461 and was employed as a portrait painter at the castle of Pavia in 1469. That same year he moved to Ferrara, where he worked until 1474 and between 1497 and 1504. He was employed as a court painter, celebrated for his portraits and equal in status to Cosimo Tura (c. 1430-1495). Only one certain work by him has survived, a portrait of Tito V. Strozzi now at the Cini Foundation, Venice. Both of his two known medals portray Ercole d'Este, duke of Ferrara and are signed and dated 1472. Baldassare lived in Este territory until after 1506, the likely time period of his death.
 Eduardo Arslan, "Baldassarre d'Este," in Dizionario Biografico degli italiani, vols. in progress, 5(1963): 444, repeats the suggestion of Baldassare being a bastard son of Niccolò III d'Este; Eberhard Ruhmer, "Baldassare d'Este--ein Problem und seine warscheinlichste Lösung," Pantheon 25 (1967): 250-258, expresses his doubts on the point. Kristen Lippincott, "Baldassare d'Este," in Dictionary of Art, Ed. Jane Turner, 34 vols., London and New York, 1996: 3:93, mentions a document of 1489 in which he is recorded as the illegitimate son of Niccolò III.
Venturi, Adolfo. "Baldassare Estense." In Thieme-Becker 1907-1950, 2:387-389.
Cook, Herbert. "Further Light on Baldassare d'Este." The Burlington Magazine 27 (June 1915): 98-104.
Longhi, Roberto. Officina ferrarese (1934), seguíta dagli Ampliamenti (1940) e dai Nuovi ampliamenti (1940-1955). Florence, 1956: 48-51, 137-138, 182-184.