Examples
Worked examples
- Is an instance
A statistician named as co-I on a clinical trial, responsible for the analytic workstream with a named budget line
Counter-examples
Looks similar, but isn't
- Not an instance
A collaborator who provided a unique reagent but is not on the grant is not a co-investigator
Editorial commentary
Co-investigator status carries scientific responsibility but not the lead-PI’s ultimate accountability for the whole project. The role is distinct from collaborator (who provides resources or input but has no formal responsibility) and from consultant (who advises against a fee).
References
- NIH Multiple Principal Investigator Policy
- UKRI Co-Investigator Eligibility
Frequently Asked Questions
What is a co-investigator in research?
A co-investigator is a named investigator on a research grant, contract, or protocol — other than the lead principal investigator (PI) — who contributes substantive scientific expertise and shares responsibility for part of the work, typically with a defined role in the proposal and a named budget allocation.
Does a co-investigator carry the same accountability as the principal investigator?
No. A co-investigator carries scientific responsibility for their portion of the project, but not the lead PI’s ultimate accountability for the project as a whole.
What is the difference between a co-investigator and a collaborator?
A co-investigator has a formally defined role and budget allocation on the grant and shares scientific responsibility for part of the work. A collaborator, by contrast, provides resources or input to the project but has no formal responsibility — for example, someone who supplies a unique reagent but isn’t named on the grant is a collaborator, not a co-investigator.
How does a co-investigator differ from a consultant?
A consultant advises on a project in exchange for a fee, but does not hold the scientific responsibility or formal named role that a co-investigator has.
Are “co-PI” and “co-investigator” the same thing?
CASRAI lists “Co-PI” and “Co-I” as aliases for co-investigator, so the terms are often used interchangeably in practice. Usage can still vary by funder and institution, so it is worth checking the specific policy that applies to a given grant.
Also known as
Co-PI · Co-I
Machine-readable encodings
Use in your systems
<role vocab="credit"
vocab-identifier="https://casrai.org/dictionary/"
vocab-term="Co-investigator"
vocab-term-identifier="https://casrai.org/dictionary/term/co-investigator" />{
"@context": "https://schema.org",
"@type": "DefinedTerm",
"@id": "https://casrai.org/dictionary/term/co-investigator",
"name": "Co-investigator",
"identifier": "https://casrai.org/dictionary/term/co-investigator",
"description": "A named investigator on a research grant, contract, or protocol other than the lead PI, who contributes substantive scientific expertise and shares responsibility for portions of the work, typically with a defined role in the proposal and a named budget allocation.",
"inDefinedTermSet": "https://casrai.org/dictionary/domain/mentorship-career-stages#set",
"url": "https://casrai.org/dictionary/term/co-investigator",
"sameAs": [
"Co-PI",
"Co-I"
],
"license": "https://creativecommons.org/licenses/by/4.0/",
"publisher": {
"@id": "https://casrai.org/#organization"
},
"author": {
"@id": "https://casrai.org/#editorial-team"
},
"datePublished": "2026-05-21T02:01:54",
"dateModified": "2026-08-15T04:38:31",
"inLanguage": "en-GB",
"isAccessibleForFree": true
}
