Late 1970s–1980s

Gundam models are based on the Mobile Suit Gundam franchise, which debuted in 1979 as a television show. The show was not highly successful, and the toys produced by Clover did not sell well.

In 1980, Bandai obtained the rights to produce models based on the Gundam franchise. While Clover's models were produced in the style of most children's toys - fully assembled and ready for play - Bandai designed theirs as plastic kits to be assembled, similar to military vehicle models. While Clover's products targeted children, Bandai's approach was more appealing to the teenage and adult consumers that were more typical of Mobile Suit Gundam's audience, and was received extremely well.

Nearly every mecha in the series was made into a model kit, from mobile suits to support aircraft and space battleships. Parts came in up to three different cast-in colors. These early kits are distinguished by their lack of articulation and low detail and, unlike later generations, require glue to assemble.

A later development was System Injection, a technique which permitted a single "part" to be cast in multiple colors of plastic simultaneously, minimizing the need to paint the finished model.

Mid 1980s–1990s

In 1985, Bandai introduced use of poly-caps (soft plastic, typically Polyethylene) as connectors for better articulation of joints.

The 1987 model line for Gundam Sentinel introduced snap-fit models, which needed little or no glue to assemble. This would become standard in 1988, after which all kits use snap-fit assembly and no glue is needed.

In 1990, Bandai introduced the High Grade (HG) line, which began an ongoing process of increasing model quality, and the creation of a grade system to describe the detail and quality of each kit. HG kits had much higher detail and articulation, as well as features normally found in larger-scale models, despite being 1:144 scale. One example is the 'Gundam Core Block System', in which the pilot sits in a "Core" which can be removed from the Gundam to become a distinct vehicle, and the Zeta Gundam's transformation feature.

In 1993, a unified set of poly-cap joints was created for smaller scale models that allowed easy mass production of models that all shared the same basic skeletal frame. This standardization allowed Bandai to release more models over a shorter period. As a result, the Gundam shows of the 1990s usually received sizable 1:144 model lines.

In 1995, the 1:100 scale Master Grade (MG) line was introduced. This line featured more parts, better detail and improved articulation than past kits of the same scale.

In 1998, Bandai introduced the 1:60 Perfect Grade (PG) line. This line features extensive detail and articulation, light-up features, and a "body on frame" skeletal system in which the exterior panels of the model are separate components attached to a completely functional, articulated internal frame. This design element would later appear (sometimes in a limited form) in lower-grade models. The PG line is typically the most expensive among all Gunpla kits, and only a select few mobile suits have been released in this line.

In 1999, to celebrate the 20th anniversary of the franchise, Bandai released 1:144 First Grade (FG) kits of mobile suits from the original series. Marketed as budget models, these snap-fit kits featured the simplicity of the original kits, but with more modern designs based upon the corresponding Perfect Grade kits.

2000s

For the Mobile Suit Gundam SEED models a new type of non-graded (NG) 1:144 model was introduced, with a completely different design plan. While these still feature snap-fit and color molding, they omit major joints, opting instead to only allow critical pieces to move—typically the neck, hips, shoulders, and feet. These are budget models, usually retailing much lower than other models; and this line was extensive, covering nearly every machine to be featured in that TV series.

Gundam SEED also featured non graded 1:100 models, identical in quality to Bandai's High Grade offerings.

It was also during this decade that the term "Gunpla" was coined by Bandai.

2010s

In 2010, Bandai released the 1:48 Mega Size Model RX-78-2 Gundam kit as part of the franchise's 30th anniversary campaign. This kit features many innovations that make it easy to assemble for first-time Gunpla collectors. For example, the parts are attached to sprue gates thin enough to break without the need to use of plastic cutters, and excess gate plastic can be removed from the parts without using a hobby knife. Some sprues have been designed to snap together for easy and quick removal of assembled parts.

In the same year, Bandai introduced the 1:144 Real Grade (RG) line, which takes design elements from the MG line such as an inner skeletal frame to improve upon the HG line.

Both Mega Size Model and RG variants of the RX-78-2 Gundam were patterned after the 1/1 scale Gundam statue on display in Odaiba. Bandai also released Ecopla, a series of High Grade Universal Century (HGUC) and super deformed (SD) kits molded in black and made entirely out of recycled sprues.

In 2011, Bandai released the Entry Grade (EG) line, a low-cost model series similar to the 1:144 NG and FG lines, sold only in parts of Asia. Unlike other kits of the same scale, the first line of EG kits were made in China and the series was initially discontinued until the line was rebooted in 2020 with kits from non-Gundam franchises.

Also in 2011, Bandai introduced the Advanced Grade (AG) line, a budget line that focuses more on the arrangement of colored parts, thus sacrificing more articulation than the previous budget lines. The AG line incorporates a microchip that enables collectors to use the kit in the Gage-ing arcade game.

In 2014, as part of the 35th anniversary celebration of Gundam, Bandai released the MG RX-78-2 Gundam ver. 3.0, which incorporates the engineering techniques used in the MG 2.0 and RG kits.

In 2015, Bandai introduced a sub-line of the HG called "HG Revive", which consists of re-engineered 1:144 scale kits of the RX-78-2 Gundam and other classic mobile suit designs.

From late 2016 onwards, every Bandai produced model kit, including Gunpla, were made with Japanese and English text on the box and manuals.

In 2017, Bandai began the Gundam Evolution Project, which sought to improve Gunpla technology with various groundbreaking kits, such as the adoption of a new joint system or a new LED system for large-scale kits. This was in preparation for the 40th anniversary of Gunpla in 2020.